Income Taxes (Income Tax Computed by Applying U.S. Federal Statutory Income Tax Rate) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax expense computed at the statutory rate	$ 111,930	$ 117,608	$ 101,808
Effect of tax-exempt interest	(70,889)	(58,761)	(46,535)
Bank owned life insurance income	(1,255)	(1,116)	(1,086)
Other	685	316	(1,172)
Income tax expense, as reported	$ 40,471	$ 58,047	$ 53,015