Other Assets (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Tax Cut and Jobs Act of 2017, Income Tax Effect	$ 765
Proportional amortization as a component of income tax expense	3,100	$ 1,800
Affordable housing tax credits and other tax benefits, amount	3,000	2,400
Tax Credit Carryforward [Line Items]
Capital commitments relating to investments	18,200	12,700
Low Income Housing Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	$ 7,100	$ 7,900