Goodwill and Other Intangible Assets (Aggregate Amortization Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	$ 22,417	$ 19,781	$ 24,184
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	19,442	16,411	18,031
Credit Card and Trust Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	1,975	2,172	2,369
Trade Name [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense			2,388
Merchant Processing Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Aggregate amortization expense	$ 1,000	$ 1,198	$ 1,396