Goodwill and Other Intangible Assets (Carrying Value of Intangible Assets Subject to Amortization) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Purchase Value	$ 307,417	$ 275,917
Accumulated Amortization	200,610	179,766
Carrying Value	106,807	96,151
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	247,455	215,955
Accumulated Amortization	168,577	151,446
Carrying Value	78,878	64,509
Credit Card and Trust Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	49,962	49,962
Accumulated Amortization	22,448	19,564
Carrying Value	27,514	30,398
Merchant Processing Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	10,000	10,000
Accumulated Amortization	9,585	8,756
Carrying Value	$ 415	$ 1,244