Income Taxes - Summary of Income Tax Expense and Effective Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 14,080	$ 14,109	$ 28,700	$ 31,516
Effective tax rate	18.80%	16.10%	12.70%	14.90%