Earnings Per Common Share - Computations of Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income available to common equity	$ 1,233,844	$ 998,397	$ 990,368
Less: Income attributable to unvested stock-based compensation awards	(10,363)	(10,673)	(11,787)
Net income available to common shareholders	$ 1,223,481	$ 987,724	$ 978,581
Adjusted weighted-average shares outstanding:
Common and unvested stock-based compensation awards	158,121	138,285	132,532
Less: Unvested stock-based compensation awards	(1,341)	(1,482)	(1,582)
Plus: Incremental shares from assumed conversion of stock-based compensation awards and warrants to purchase common stock	524	730	894
Adjusted weighted-average shares outstanding	157,304	137,533	131,844
Diluted earnings per common share	$ 7.78	$ 7.18	$ 7.42