Commitments and Contingencies Narrative (Details) $ in Thousands		12 Months Ended
	Mar. 31, 2016 USD ($) defendant plaintiff	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Residential mortgage principal balance repurchase request received		$ 543
Residential mortgage principal balance FHLB credit enhancement		84,000
Residential mortgage repurchase reserves FHLB credit enhancement		1,200	$ 1,700
Agostino, et al. v. Ameriprise Financial Services, Inc
Loss Contingencies [Line Items]
Number of unrelated defendants | defendant	2
Amount alleged in damages	$ 11,300
Reserve for Off-balance Sheet Activities
Loss Contingencies [Line Items]
Valuation allowances and reserves		368,774	395,260
Reserve for Off-balance Sheet Activities | Residential Mortgage
Loss Contingencies [Line Items]
Valuation allowances and reserves		$ 2,100	$ 2,500
Pending Litigation [Member] | Agostino, et al. v. Ameriprise Financial Services, Inc
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff	67