Consolidated Statements of Comprehensive Income Statement - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 491,795	$ 468,532	$ 419,930
Other comprehensive income (loss), net of tax:
Unrealized holding gains (losses) arising during period from securities available for sale	(16,635)	61,284	(108,490)
Less: reclassification adjustment for net gains on sale of securities available for sale in net income	52,065	34,352	19,970
Net change in unrealized holding gains (losses) on securities available for sale	(68,700)	26,932	(128,460)
Change in unamortized net holding losses on investment securities held to maturity	7,905	9,027	10,591
Less: non-credit related impairment on investment securities held to maturity	55	151	2,065
Change in unamortized non-credit related impairment on investment securities held to maturity	134	1,871	1,520
Net change in unamortized holding losses on securities held to maturity	7,984	10,747	10,046
Unrealized holding gains (losses) arising during period from cash flow hedge instruments	811	(1,900)	8,098
Change in defined benefit plans	11,955	800	(3,678)
Other comprehensive income (loss), net of tax	(47,950)	36,579	(113,994)
Comprehensive income	443,845	505,111	305,936
Less: comprehensive income attributable to noncontrolling interests	2,228	1,976	2,094
Comprehensive income attributable to shareholder	$ 441,617	$ 503,135	$ 303,842