Parent Company Information (Components of Condensed Balance Sheets The Parent Company) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets:
Cash and due from banks	$ 190,663	$ 199,693	$ 213,914	$ 205,921
Securities available-for-sale, at fair value	2,991,091	2,984,631
Other assets	294,462	343,856
Total assets	26,072,529	24,641,118
Liabilities and shareholders’ equity:
Total liabilities	23,545,517	22,227,158
Total liabilities and shareholders' equity	26,072,529	24,641,118
Parent Company [Member]
Assets:
Cash and due from banks	152,947	279,644	$ 272,492	$ 273,573
Securities available-for-sale, at fair value	0	2,578
Intercompany debt securities	150,000	0
Investment in subsidiaries	2,425,398	2,345,457
Alternative investments	4,275	6,795
Other assets	24,659	15,263
Total assets	2,757,279	2,649,737
Liabilities and shareholders’ equity:
Senior notes	148,194	147,940
Junior subordinated debt	77,320	77,320
Accrued interest payable	2,589	2,591
Due to subsidiaries	365	48
Other liabilities	1,799	7,878
Total liabilities	230,267	235,777
Shareholders’ equity	2,527,012	2,413,960
Total liabilities and shareholders' equity	$ 2,757,279	$ 2,649,737