Income Taxes (Provision for Income Taxes) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Current Federal Tax Expense (Benefit)	$ 49,582	$ 168,164	$ 187,056
Current State and Local Tax Expense (Benefit)	3,103	12,112	22,631
Current Foreign Tax Expense (Benefit)	2,455	0	0
Current Income Tax Expense (Benefit)	55,140	180,276	209,687
Deferred Federal Income Tax Expense (Benefit)	(8,476)	16,910	(29,095)
Deferred State and Local Income Tax Expense (Benefit)	147	157	(1,564)
Deferred Foreign Income Tax Expense (Benefit)	(1,100)	0	0
Deferred Income Tax Expense (Benefit)	(9,429)	17,067	(30,659)
Income Tax Expense (Benefit)	$ 45,711	$ 197,343	$ 179,028