Income Taxes - Income Taxes Expense from Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current income tax (benefit) expense	$ 138,262	$ 132,806	$ 174,284
Deferred income tax (benefit) expense	(765,877)	99,839	75,610
Income tax expense (benefit) from continuing operations	$ (627,615)	$ 232,645	$ 249,894