Income Taxes - Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Components Of Income Tax Expense Benefit Continuing Operations [Abstract]
Income tax expense (benefit)	$ 112,395	$ (41,976)
Effective tax rate	39.80%	30.90%