Income Taxes (Income Tax Expense) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current income tax expense	$ 840	$ 58,707	$ 48,748
Deferred income tax expense (benefit)	52,923	(14,493)	(11,598)
Income tax expense, as reported	$ 53,763	$ 44,214	$ 37,150
Effective tax rate	10.60%	10.80%	10.90%