Fair Value Measurements - Quantitative Information about Recurring Level 3 Fair Value Financial Instruments (Details) - Recurring - Level 3 $ in Millions	Dec. 31, 2019 USD ($) orgination_pull-through_rate_per_loan $ / loan option_adjusted_spread_per_loan discount_rate_per_loan constant_default_rate_per_loan constant_prepayment_rate_per_loan	Dec. 31, 2018 USD ($) orgination_pull-through_rate_per_loan $ / loan option_adjusted_spread_per_loan discount_rate_per_loan constant_default_rate_per_loan constant_prepayment_rate_per_loan
Home equity
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held-for-investment | $	$ 2	$ 2
Home equity | Discount rate | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage) | discount_rate_per_loan	0.072	0.072
Home equity | Discount rate | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage) | discount_rate_per_loan	0.108	0.108
Home equity | Discount rate | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage) | discount_rate_per_loan	0.090	0.090
Home equity | Constant prepayment rate | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage)	0.130	0.136
Home equity | Constant prepayment rate | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage)	0.195	0.203
Home equity | Constant prepayment rate | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage)	0.162	0.169
Home equity | Constant default rate | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage) | constant_default_rate_per_loan	0.027	0.030
Home equity | Constant default rate | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage) | constant_default_rate_per_loan	0.040	0.046
Home equity | Constant default rate | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Loans held for investment, fair value input (in percentage) | constant_default_rate_per_loan	0.033	0.038
Mortgage servicing rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Mortgage servicing rights | $	$ 291	$ 290
Mortgage servicing rights | Constant prepayment rate | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan)	0.000	0.000
Mortgage servicing rights | Constant prepayment rate | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan)	0.123	0.107
Mortgage servicing rights | Constant prepayment rate | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan)	0.106	0.096
Mortgage servicing rights | Option adjusted spread | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan) | option_adjusted_spread_per_loan	0.024	0.021
Mortgage servicing rights | Option adjusted spread | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan) | option_adjusted_spread_per_loan	0.204	0.259
Mortgage servicing rights | Option adjusted spread | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan) | option_adjusted_spread_per_loan	0.053	0.054
Mortgage servicing rights | Weighted average cost to service per loan | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan) | $ / loan	67	67
Mortgage servicing rights | Weighted average cost to service per loan | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan) | $ / loan	95	95
Mortgage servicing rights | Weighted average cost to service per loan | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Weighted average cost to service per loan (in dollars per loan) | $ / loan	84	86
Rate lock commitments
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Derivative assets | $	$ 34	$ 20
Rate lock commitments | Origination pull-through rate | Range (Weighted Average)
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Rate lock commitment, fair value input (in percentage) | orgination_pull-through_rate_per_loan	0.800	0.750
Rate lock commitments | Origination pull-through rate | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Rate lock commitment, fair value input (in percentage) | orgination_pull-through_rate_per_loan	0.872	0.872
Rate lock commitments | Origination pull-through rate | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Rate lock commitment, fair value input (in percentage) | orgination_pull-through_rate_per_loan	0.815	0.768
DOJ litigation settlement
Fair Value Inputs, Assets and Liabilities, Quantitative Information
DOJ litigation settlement | $	$ (35)	$ (60)
Contingent consideration
Fair Value Inputs, Assets and Liabilities, Quantitative Information
Contingent consideration | $	$ (10)	$ (6)