Condensed Financial Information - Parent Company Only Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets [Abstract]
Other assets	$ 620,059	$ 550,017
Investments in:
Total Assets	18,944,247	17,914,718
Other liabilities	329,916	282,578
Total Liabilities	16,823,132	15,872,824
Shareholders' Equity [Abstract]
Shareholders’ equity	2,121,115	2,041,894	$ 1,996,665	$ 2,063,187
Total Liabilities and Shareholders’ Equity	18,944,247	17,914,718
Parent
Assets [Abstract]
Cash	8,568	0	$ 137	$ 8
Other assets	5,648	4,337
Receivable from subsidiaries	46,715	29,249
Investments in:
Bank subsidiaries	2,265,264	2,226,975
Non-bank subsidiaries	417,615	408,187
Total Assets	2,743,810	2,668,748
Long-term debt	362,005	361,504
Payable to non-bank subsidiaries	183,152	188,087
Other liabilities	77,538	77,263
Total Liabilities	622,695	626,854
Shareholders' Equity [Abstract]
Shareholders’ equity	2,121,115	2,041,894
Total Liabilities and Shareholders’ Equity	$ 2,743,810	$ 2,668,748