Variable Interest Entities (Schedules) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Low Income Housing Tax Credit Partnerships
Variable Interest Entity [Line Items]
Proportional amortization method investments included in other assets	$ 58,343	$ 0
Equity method investments included in other assets	1,725	26,495
Cumulative equity investments in LIHTC partnerships	46,659	34,065
Unfunded commitments included in other liabilities	39,994	17,420
Short-term construction loans and letter of credit commitments	7,180	0
Funded portion of short-term loans and letters of credit	0	0
Proportional amortization expense recognized as a component of income tax expense	1,820	0	$ 0
Income from equity method investments recognized as a component of non-interest income	(1,648)	389	553
Real Estate Partnerships
Variable Interest Entity [Line Items]
Equity method investments included in other assets	6,468	6,822
Unfunded commitments included in other liabilities	0	0
Income from equity method investments recognized as a component of non-interest income	$ 1,584	$ 1,040	$ 1,212