Fair Value Measurements - Quantitative Information about Recurring Level 3 Fair Value Instruments (Details) - Fair Value - Level 3 $ in Millions	Mar. 31, 2020 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, 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
Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment | $	$ 2	$ 2
Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset | $	223	291
Rate lock commitments (net)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset | $	169	34
DOJ Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Litigation settlement at fair value | $	35	35
Contingent consideration
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration | $	$ 16	$ 10
Discount rate | Minimum | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | discount_rate_per_loan	0.072	0.072
Discount rate | Maximum | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | discount_rate_per_loan	0.108	0.108
Discount rate | Weighted Average | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | discount_rate_per_loan	0.090	0.090
Constant prepayment rate | Minimum | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | constant_prepayment_rate_per_loan	0.064	0.130
Constant prepayment rate | Minimum | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | constant_prepayment_rate_per_loan	0.000	0.000
Constant prepayment rate | Maximum | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | constant_prepayment_rate_per_loan	0.094	0.195
Constant prepayment rate | Maximum | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | constant_prepayment_rate_per_loan	0.148	0.123
Constant prepayment rate | Weighted Average | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage)	0.078	0.162
Constant prepayment rate | Weighted Average | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | constant_prepayment_rate_per_loan	0.120	0.106
Default rate | Minimum | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | constant_default_rate_per_loan	0.022	0.027
Default rate | Maximum | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | constant_default_rate_per_loan	0.033	0.040
Default rate | Weighted Average | Home equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment, fair value input (in percentage) | constant_default_rate_per_loan	0.028	0.033
Option volatility | Minimum | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | option_adjusted_spread_per_loan	0.036	0.024
Option volatility | Maximum | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | option_adjusted_spread_per_loan	0.199	0.204
Option volatility | Weighted Average | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | option_adjusted_spread_per_loan	0.056	0.053
Weighted average cost to service per loan | Minimum | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | $ / loan	67	67
Weighted average cost to service per loan | Maximum | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | $ / loan	95	95
Weighted average cost to service per loan | Weighted Average | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing asset, measurement input | $ / loan	85	84
Origination pull-through rate | Minimum | Rate lock commitments (net)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, measurement input (in percentage) | orgination_pull-through_rate_per_loan	0.800	0.750
Origination pull-through rate | Maximum | Rate lock commitments (net)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, measurement input (in percentage) | orgination_pull-through_rate_per_loan	0.872	0.872
Origination pull-through rate | Weighted Average | Rate lock commitments (net)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset, measurement input (in percentage) | orgination_pull-through_rate_per_loan	0.819	0.768