| Income Taxes (Tables)
 | 12 Months Ended | 
| Dec. 31, 2015 | 
|---|
| Income Tax Disclosure [Abstract] |  | 
| Schedule of Provision for Income Taxes | 
 
 The provision for income taxes consists of the following (in
 thousands): 
   
 
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  
 |  |  | Year Ended December 31, |  |  
 |  |  | 2015 |  |  | 2014 |  |  | 2013 |  |  
 | 
 Income before provision for income taxes: |  |  |  |  |  |  |  |  |  |  |  |  |  
 | 
 United States |  | $ | 116,448 |  |  | $ | 84,797 |  |  | $ | 22,684 |  |  
 | 
 Foreign |  |  | (3,080 | ) |  |  | (1,814 | ) |  |  | (743 | ) |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 |  |  | $ | 113,368 |  |  | $ | 82,983 |  |  | $ | 21,941 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 | 
 The provision (benefit) for income taxes consists of the
 following (in thousands): |  |  |  |  |  |  |  |  |  |  |  |  |  
 | 
 Federal: |  |  |  |  |  |  |  |  |  |  |  |  |  
 | 
 Current |  | $ | 39,895 |  |  | $ | 28,452 |  |  | $ | 20,245 |  |  
 | 
 Deferred |  |  | (1,853 | ) |  |  | (566 | ) |  |  | (8,077 | ) |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 |  |  |  | 38,042 |  |  |  | 27,886 |  |  |  | 12,168 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 | 
 State: |  |  |  |  |  |  |  |  |  |  |  |  |  
 | 
 Current |  |  | 7,058 |  |  |  | 4,123 |  |  |  | 2,522 |  |  
 | 
 Deferred |  |  | 1,918 |  |  |  | 1,443 |  |  |  | (1,199 | ) |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 |  |  |  | 8,976 |  |  |  | 5,566 |  |  |  | 1,323 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 | 
 Foreign: |  |  |  |  |  |  |  |  |  |  |  |  |  
 | 
 Current |  |  | — |  |  |  | — |  |  |  | 244 |  |  
 | 
 Deferred |  |  | — |  |  |  | — |  |  |  | — |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 |  |  |  | — |  |  |  | — |  |  |  | 244 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 |  |  | $ | 47,018 |  |  | $ | 33,452 |  |  | $ | 13,735 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  | 
| Significant Components of Deferred Tax Assets (Liabilities), Net | 
 
 Significant components of the Company’s deferred tax assets,
 net consisted of the following (in thousands): 
   
 
 |  |  |  |  |  |  |  |  |  |  
 |  |  | Year Ended December 31, |  |  
 |  |  | 2015 |  |  | 2014 |  |  
 | 
 Deferred tax assets: |  |  |  |  |  |  |  |  |  
 | 
 Accrued expenses and bonuses |  | $ | 1,787 |  |  | $ | 5,435 |  |  
 | 
 Bad debt and other reserves |  |  | 2,178 |  |  |  | 2,009 |  |  
 | 
 Deferred compensation |  |  | 15,405 |  |  |  | 8,872 |  |  
 | 
 Stock-based compensation |  |  | 15,984 |  |  |  | 19,707 |  |  
 | 
 Deferred rent |  |  | 1,735 |  |  |  | 1,321 |  |  
 | 
 Unrealized gain on foreign currency |  |  | — |  |  |  | 56 |  |  
 | 
 Net operating and capital loss carryforwards . |  |  | 1,281 |  |  |  | 680 |  |  
 | 
 Fixed assets and leasehold improvements |  |  | — |  |  |  | 203 |  |  
 | 
 Other comprehensive income |  |  | 382 |  |  |  | — |  |  
 | 
 State taxes |  |  | 496 |  |  |  | — |  |  
 |  |  |   |   |  |  |   |   |  |  
 | 
 Deferred tax assets before valuation allowance |  |  | 39,248 |  |  |  | 38,283 |  |  
 | 
 Valuation allowance |  |  | (1,311 | ) |  |  | (728 | ) |  
 |  |  |   |   |  |  |   |   |  |  
 |  |  | $ | 37,937 |  |  | $ | 37,555 |  |  
 |  |  |   |   |  |  |   |   |  |  
 | 
 Deferred Tax Liabilities: |  |  |  |  |  |  |  |  |  
 | 
 Fixed assets and leasehold improvements |  | $ | (1,521 | ) |  | $ | — |  |  
 | 
 Prepaid expenses |  |  | (1,131 | ) |  |  | (1,392 | ) |  
 | 
 Other comprehensive income |  |  | — |  |  |  | (113 | ) |  
 | 
 State taxes |  |  | — |  |  |  | (1,185 | ) |  
 |  |  |   |   |  |  |   |   |  |  
 |  |  |  | (2,652 | ) |  |  | (2,690 | ) |  
 |  |  |   |   |  |  |   |   |  |  
 |  |  | $ | 35,285 |  |  | $ | 34,865 |  |  
 |  |  |   |   |  |  |   |   |  |  | 
| Components of Provision for Income Taxes and Income before Provision for Income Taxes | 
 
 The provision for income taxes differs from the amount computed by
 applying the statutory federal corporate income tax rate of 35% to
 income before provision for income taxes and consisted of the
 following (in thousands): 
   
 
 |  |  |  |  |  |  |  |  |  |  |  |  |  |  
 |  |  | Year Ended
 December 31, |  |  
 |  |  | 2015 |  |  | 2014 |  |  | 2013 |  |  
 | 
 Income tax expense at the federal statutory rate of 35% |  | $ | 39,679 |  |  | $ | 29,044 |  |  | $ | 7,679 |  |  
 | 
 State income tax expense, net of federal benefit |  |  | 4,569 |  |  |  | 3,622 |  |  |  | 985 |  |  
 | 
 Effect of state tax rate change on deferred taxes |  |  | 1,273 |  |  |  | — |  |  |  | — |  |  
 | 
 Permanent differences related to compensation charges, net of
 federal benefit |  |  | 81 |  |  |  | 163 |  |  |  | 3,445 |  |  
 | 
 Change in valuation allowance |  |  | 583 |  |  |  | 442 |  |  |  | 86 |  |  
 | 
 Differences due to tax-sharing agreement |  |  | — |  |  |  | — |  |  |  | 1,265 |  |  
 | 
 Other |  |  | 833 |  |  |  | 181 |  |  |  | 275 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |  
 |  |  | $ | 47,018 |  |  | $ | 33,452 |  |  | $ | 13,735 |  |  
 |  |  |   |   |  |  |   |   |  |  |   |   |  |