Goodwill and Intangible Assets (Carrying Amounts) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying amount of intangible assets
Gross carrying amount	$ 53,135	$ 38,357
Accumulated amortization	37,574	36,750
Net carrying amount	15,561	1,607
Core Deposits
Carrying amount of intangible assets
Gross carrying amount	48,834	38,357
Accumulated amortization	37,403	36,750
Net carrying amount	11,431	$ 1,607
Mortgage servicing rights
Carrying amount of intangible assets
Gross carrying amount	4,301
Accumulated amortization	171
Net carrying amount	$ 4,130