Quarterly report pursuant to Section 13 or 15(d)

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

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Income Taxes - Components of Provision for Income Taxes and Income before Provision for Income Taxes (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Income Tax Disclosure [Abstract]        
Income tax expense at the federal statutory rate of 35%, amount $ 8,967 $ 10,173 $ 15,793 $ 18,817
State income tax expense, net of federal benefit, amount 973 1,153 1,741 2,139
Foreign rate differential, amount 25 48 47 107
Windfall tax benefits, net related to stock-based compensation, amount     (156) 0
Change in valuation allowance, amount 62 120 116 266
Other, amount 25 48 13 95
Provision for income taxes, amount $ 10,052 $ 11,542 $ 17,554 $ 21,424
Income tax expense at the federal statutory rate of 35%, rate 35.00% 35.00% 35.00% 35.00%
State income tax expense, net of federal benefit, rate 3.80% 4.00% 3.90% 4.00%
Foreign rate differential, rate 0.10% 0.20% 0.10% 0.20%
Windfall tax benefits, net related to stock-based compensation, rate     (0.40%) 0.00%
Change in valuation allowance, rate 0.20% 0.40% 0.30% 0.50%
Other, rate 0.10% 0.10% 0.00% 0.10%
Provision for income taxes, rate 39.20% 39.70% 38.90% 39.80%