Fair Value Measurements (Level 3 Quantitative Information) (Details) - Level 3 - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Mortgage servicing rights | Weighted Average
Fair Value Inputs [Abstract]
Constant prepayment rate (as a percent)	9.40%	16.70%
Recurring
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	$ 215	$ 418	$ 394	$ 466	$ 437	$ 428
Fair value, Liabilities	83	60	60
Recurring | Litigation settlement
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Liabilities	60	60	60	84	84	84
Recurring | Contingent consideration
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Liabilities	23	0	0
Recurring | Home equity
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	5	65	5	82	95	106
Recurring | Mortgage servicing rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	184	335	295	301	281	296
Recurring | Rate lock commitments
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	26	18	$ 41	$ 83	$ 61	$ 26
Recurring | Discounted cash flows | Litigation settlement
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Liabilities	$ 60	$ 60
Recurring | Discounted cash flows | Litigation settlement | Lower range
Fair Value Inputs [Abstract]
Discount rate (as a percent)	7.20%	6.60%
Recurring | Discounted cash flows | Litigation settlement | Upper range
Fair Value Inputs [Abstract]
Discount rate (as a percent)	10.80%	9.80%
Recurring | Discounted cash flows | Litigation settlement | Weighted Average
Fair Value Inputs [Abstract]
Discount rate (as a percent)	9.00%	8.20%
Recurring | Discounted cash flows | Contingent consideration
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Liabilities	$ 23
Recurring | Discounted cash flows | Contingent consideration | Lower range
Fair Value Inputs [Abstract]
Fair value input, beta	0.60%
Fair value inputs, equity volatility	26.60%
Recurring | Discounted cash flows | Contingent consideration | Upper range
Fair Value Inputs [Abstract]
Fair value input, beta	1.00%
Fair value inputs, equity volatility	58.90%
Recurring | Discounted cash flows | Contingent consideration | Weighted Average
Fair Value Inputs [Abstract]
Fair value input, beta	1.10%
Fair value inputs, equity volatility	40.00%
Recurring | Discounted cash flows | Home equity
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	$ 5	$ 65
Recurring | Discounted cash flows | Home equity | Lower range
Fair Value Inputs [Abstract]
Discount rate (as a percent)	5.80%	6.00%
Constant prepayment rate (as a percent)	5.00%	16.30%
CDR rate (as a percent)	3.00%	2.70%
Recurring | Discounted cash flows | Home equity | Upper range
Fair Value Inputs [Abstract]
Discount rate (as a percent)	10.80%	12.20%
Constant prepayment rate (as a percent)	7.50%	24.40%
CDR rate (as a percent)	4.50%	4.10%
Recurring | Discounted cash flows | Home equity | Weighted Average
Fair Value Inputs [Abstract]
Discount rate (as a percent)	9.00%	9.30%
Constant prepayment rate (as a percent)	6.30%	20.30%
CDR rate (as a percent)	3.40%	3.70%
Recurring | Discounted cash flows | Mortgage servicing rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	$ 184	$ 335
Recurring | Discounted cash flows | Mortgage servicing rights | Lower range
Fair Value Inputs [Abstract]
Discount rate (as a percent)	5.20%	6.20%
Constant prepayment rate (as a percent)	7.60%	13.90%
Weighted average cost to service per loan	$ 56	$ 55
Recurring | Discounted cash flows | Mortgage servicing rights | Upper range
Fair Value Inputs [Abstract]
Discount rate (as a percent)	7.70%	9.30%
Constant prepayment rate (as a percent)	11.20%	19.20%
Weighted average cost to service per loan	$ 82	$ 82
Recurring | Discounted cash flows | Mortgage servicing rights | Weighted Average
Fair Value Inputs [Abstract]
Discount rate (as a percent)	6.40%	7.80%
Constant prepayment rate (as a percent)	9.40%	16.70%
Weighted average cost to service per loan	$ 70	$ 68
Recurring | Discounted cash flows | Rate lock commitments | Lower range
Fair Value Inputs [Abstract]
Asset growth rate (as a percent)	1.00%	4.20%
Recurring | Discounted cash flows | Rate lock commitments | Upper range
Fair Value Inputs [Abstract]
Asset growth rate (as a percent)	18.10%	11.60%
Recurring | Discounted cash flows | Rate lock commitments | Weighted Average
Fair Value Inputs [Abstract]
Asset growth rate (as a percent)	3.70%	7.90%
Recurring | Consensus pricing | Rate lock commitments
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value, Assets	$ 26	$ 18
Recurring | Consensus pricing | Rate lock commitments | Lower range
Fair Value Inputs [Abstract]
Origination pull-through rate (as a percent)	66.60%	66.90%
Recurring | Consensus pricing | Rate lock commitments | Upper range
Fair Value Inputs [Abstract]
Origination pull-through rate (as a percent)	100.00%	100.00%
Recurring | Consensus pricing | Rate lock commitments | Weighted Average
Fair Value Inputs [Abstract]
Origination pull-through rate (as a percent)	83.30%	83.60%