Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Current income tax expense	$ 13,824	$ 15,830
Deferred income tax expense (benefit)	(4,395)	(3,748)
Income tax expense, as reported	$ 9,429	$ 12,082
Effective tax rate	12.10%	14.30%