Goodwill and Other Intangible Assets (Carrying Value of Intangible Assets Subject to Amortization) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Purchase Value	$ 275,917	$ 248,355
Accumulated Amortization	179,766	157,715
Carrying Value	96,151	90,640
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	215,955	215,955
Accumulated Amortization	151,446	132,878
Carrying Value	64,509	83,077
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	49,962	22,400
Accumulated Amortization	19,564	16,882
Carrying Value	30,398	5,518
Merchant Processing Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	10,000	10,000
Accumulated Amortization	8,756	7,955
Carrying Value	$ 1,244	$ 2,045