Mortgage Servicing Rights - Significant Economic Assumptions (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fixed
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Weighted-average OAS	4.63%	4.52%
Weighted-average life, in years	4 years 4 months 13 days	4 years 6 months 10 days
Adjustable
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Weighted-average OAS	7.73%	7.61%
Weighted-average life, in years	3 years 2 months 8 days	2 years 11 months 12 days