Other Assets (Balances) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Assets [Abstract]
Federal Reserve Bank and FHLB Stock	$ 185,225	$ 159,443
Accrued interest receivable	89,425	80,036
Investments in low income housing tax credit partnerships	83,736	60,068
Accounts receivable	80,271	43,878
Prepaid expenses	38,035	33,298
Derivative asset positions	19,332	11,722
Taxes receivable	13,150	46,330
Private equity investments	11,028	15,771
Other real estate	6,220	3,758
Trading account assets, at fair value	3,130	3,820
Miscellaneous other assets	74,532	55,363
Total other assets	$ 604,084	$ 513,487