Annual report pursuant to Section 13 and 15(d)

Income Taxes - Components of Provision for Income Taxes and Income before Provision for Income Taxes (Detail)

v3.8.0.1
Income Taxes - Components of Provision for Income Taxes and Income before Provision for Income Taxes (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Abstract]        
Income tax expense at the federal statutory rate of 35%, amount   $ 34,729 $ 37,485 $ 39,679
State income tax expense, net of federal benefit, amount   3,577 4,346 4,569
Effect of state rate change on deferred taxes, amount   (30) (79) 1,273
Windfall tax benefits, net of shortfalls related to stock-based compensation,amount   (2,568) 0 0
Permanent differences related to compensation charges, net of federal benefit, amount   30 39 81
Change in valuation allowance, amount   170 412 583
Effect of rate and other changes on federal deferred taxes, net due to enactment of Tax Cuts and Jobs Act, amount $ 11,600 11,644 0 0
Other, amount   150 242 833
Provision for income taxes   $ 47,702 $ 42,445 $ 47,018
Income tax expense at the federal statutory rate of 35%, rate   35.00% 35.00% 35.00%
State income tax expense, net of federal benefit, rate   3.60% 4.10% 4.00%
Effect of state rate change on deferred taxes, rate   0.00% (0.10%) 1.10%
Windfall tax benefits, net of shortfalls related to stock-based compensation   (2.60%) 0.00% 0.00%
Permanent differences related to compensation charges, net of federal benefit, rate   0.00% 0.00% 0.10%
Change in valuation allowance, rate   0.20% 0.40% 0.50%
Effect of rate and other changes on federal deferred taxes, net due to enactment of Tax Cuts and Jobs Act, rate   11.70% 0.00% 0.00%
Other, rate   0.20% 0.20% 0.80%
Provision for income taxes, rate   48.10% 39.60% 41.50%