Parent Company Information (Components of Condensed Balance Sheets The Parent Company) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets:
Cash and due from banks	$ 251,258	$ 261,544	$ 223,616	$ 252,283
Securities available-for-sale, at fair value	2,984,631	2,793,873
Other assets	328,993	301,670
Total assets	24,677,820	22,533,172	20,853,145
Liabilities and shareholders’ equity:
Total liabilities	22,262,249	20,210,357
Total liabilities and shareholders' equity	24,677,820	22,533,172
Parent Company [Member]
Assets:
Cash and due from banks	279,644	272,492	$ 273,573	$ 230,201
Securities available-for-sale, at fair value	2,578	5,902
Investment in subsidiaries	2,347,068	2,249,910
Due to subsidiaries	(48)	(165)
Alternative investments	6,795	10,046
Other assets	16,359	14,356
Total assets	2,652,396	2,552,541
Liabilities and shareholders’ equity:
Senior notes	149,036	148,917
Junior subordinated debt	77,320	77,320
Accrued interest payable	2,591	2,582
Other liabilities	7,878	907
Total liabilities	236,825	229,726
Shareholders’ equity	2,415,571	2,322,815
Total liabilities and shareholders' equity	$ 2,652,396	$ 2,552,541