Affordable Housing Projects Tax Credit Partnerships (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Net affordable housing tax credit investments and related unfunded commitments	$ 71,700	$ 66,600
Affordable Housing Tax Credit Investments, Unfunded Commitments [Abstract]
2018	13,647
2019	2,893
2020	51
2021	27
2022	33
Thereafter	802
Total Unfunded Commitments	17,453
Effective Yield Method [Abstract]
Tax Credits and Other Tax Benefits Recognized	13,569	13,996	$ 13,448
Amortization Expense in Provision for Income Taxes	8,373	7,886	7,735
Proportional Amortization Method [Abstract]
Tax credits and other tax benefits recognized	1,040	0	0
Amortization Expense in Provision for Income Taxes	$ 800	$ 0	$ 0