Income Taxes (Income Tax Computed by Applying U.S. Federal Statutory Income Tax Rate) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income tax expense computed at the statutory rate	$ 119,494	$ 111,930	$ 117,608
Effect of tax-exempt interest	(75,696)	(70,889)	(58,761)
Bank owned life insurance income	(1,260)	(1,255)	(1,116)
Net tax benefit from stock-based compensation	(5,063)	0	0
Other	(325)	685	316
Income tax expense, as reported	$ 37,150	$ 40,471	$ 58,047