Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Current income tax expense	$ 13,644	$ 16,258	$ 27,468	$ 32,088
Deferred income tax expense (benefit)	(5,238)	(3,656)	(9,633)	(7,404)
Income tax expense, as reported	$ 8,406	$ 12,602	$ 17,835	$ 24,684
Effective tax rate	10.50%	14.70%	11.30%	14.50%