Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Current income tax expense	$ 15,702	$ 13,787
Deferred income tax expense (benefit)	(4,301)	(4,395)
Income tax expense, as reported	$ 11,401	$ 9,392
Effective tax rate	11.80%	12.00%