Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Current income tax expense	$ 12,848	$ 16,960	$ 40,251	$ 49,048
Deferred income tax expense (benefit)	(1,996)	(4,830)	(11,629)	(12,234)
Income tax expense, as reported	$ 10,852	$ 12,130	$ 28,622	$ 36,814
Effective tax rate	11.90%	13.80%	11.50%	14.30%