Commitments and Contingencies Contractual commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Affordable Housing Project Investment [Member]
Long-term Purchase Commitment [Line Items]
Contractual obligation	$ 4,292	$ 4,556
Capital Addition Purchase Commitments [Member]
Long-term Purchase Commitment [Line Items]
Contractual obligation	4,512
Rochester, Minnesota [Member] | Building Construction [Member]
Long-term Purchase Commitment [Line Items]
Payments for construction in process	455
Contractual obligation	$ 6,580