Other Intangible Assets (Amortization Expense of Core Deposit Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Net carrying amount	$ 34,271	$ 40,211
Core deposit intangible assets
Carrying amount, accumulated amortization and amortization expense of core deposit intangible assets
Gross carrying amount	59,143	59,143
Accumulated amortization	24,884	18,932
Net carrying amount	$ 34,259	$ 40,211