Premises and Equipment (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016 item	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)
Depreciation expense | $		$ 8,700	$ 10,100	$ 10,600
Property, Plant and Equipment, Disposals | $		$ 3,500	100	$ 1,000
Banking center consolidation related expenses | $			$ 1,411
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Number of Real Estate Properties | item		4
Buildings classified as held-for-sale | $		$ 1,600
Bank Midwest, N.A. [Member]
Number of banking centers consolidated | item			3
Number of Real Estate Properties | item		1
Community Banks Of Colorado [Member]
Number of banking centers consolidated | item	7