Other Assets (Balances) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets [Abstract]
Cash surrender value of bank-owned life insurance	$ 540,958	$ 378,830
Federal Reserve Bank and FHLB stock	159,443	169,864
Accrued interest receivable	80,036	70,393
Investments in low income housing tax credit partnerships	60,068	26,495
Taxes receivable(1)	46,330	2,611
Accounts receivable	43,878	29,821
Prepaid expenses	33,298	35,542
Private equity investments	15,771	25,493
Derivative asset positions	11,722	20,623
Other properties held for sale	7,825	14,830
SBA/GGL servicing assets, net	4,101	4,451
Miscellaneous other assets	32,081	34,267
Total other assets	1,035,511	$ 813,220
Alternative minimum tax credits	$ 42,100