Loans Held-for-Investment - Loan Credit Quality Indicators (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment
Loans held-for-investment	$ 12,117	$ 9,078
Loans held-for-investment, net	12,129	9,088
Residential first mortgage
Financing Receivable, Recorded Investment
Loans held-for-investment	3,145	2,991
Loans held-for-investment, net	3,154	2,999
Home equity
Financing Receivable, Recorded Investment
Loans held-for-investment	1,021	729
Loans held-for-investment, net	1,024	731
Other consumer
Financing Receivable, Recorded Investment
Loans held-for-investment	729	314
Loans held-for-investment, net	729	314
Commercial portfolio segment
Financing Receivable, Recorded Investment
Loans held-for-investment, net	7,222	5,044
Commercial portfolio segment | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	6,883	4,807
Commercial portfolio segment | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	285	187
Commercial portfolio segment | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	44	49
Commercial portfolio segment | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	10	1
Commercial real estate
Financing Receivable, Recorded Investment
Loans held-for-investment	2,828	2,152
Loans held-for-investment, net	2,828	2,152
Commercial and industrial
Financing Receivable, Recorded Investment
Loans held-for-investment	1,634	1,433
Loans held-for-investment, net	1,634	1,433
Warehouse
Financing Receivable, Recorded Investment
Loans held-for-investment	2,760	1,459
Loans held-for-investment, net	2,760	1,459
Other consumer
Financing Receivable, Recorded Investment
Loans held-for-investment, net	4,907	4,044
Other consumer | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	4,836	3,971
Other consumer | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	46	51
Other consumer | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	0	0
Other consumer | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	25	22
Other consumer | Residential first mortgage
Financing Receivable, Recorded Investment
Loans held-for-investment, net	3,154	2,999
Other consumer | Residential first mortgage | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	3,107	2,952
Other consumer | Residential first mortgage | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	27	28
Other consumer | Residential first mortgage | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	0	0
Other consumer | Residential first mortgage | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	20	19
Other consumer | Home equity
Financing Receivable, Recorded Investment
Loans held-for-investment, net	1,024	731
Other consumer | Home equity | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	1,002	705
Other consumer | Home equity | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	18	23
Other consumer | Home equity | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	0	0
Other consumer | Home equity | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	4	3
Other consumer | Other consumer
Financing Receivable, Recorded Investment
Loans held-for-investment, net	729	314
Other consumer | Other consumer | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	727	314
Other consumer | Other consumer | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	1	0
Other consumer | Other consumer | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	0	0
Other consumer | Other consumer | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	1	0
Commercial portfolio segment | Commercial real estate
Financing Receivable, Recorded Investment
Loans held-for-investment, net	2,828	2,152
Commercial portfolio segment | Commercial real estate | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	2,794	2,132
Commercial portfolio segment | Commercial real estate | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	24	14
Commercial portfolio segment | Commercial real estate | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	5	5
Commercial portfolio segment | Commercial real estate | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	5	1
Commercial portfolio segment | Commercial and industrial
Financing Receivable, Recorded Investment
Loans held-for-investment, net	1,634	1,433
Commercial portfolio segment | Commercial and industrial | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	1,533	1,351
Commercial portfolio segment | Commercial and industrial | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	72	53
Commercial portfolio segment | Commercial and industrial | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	24	29
Commercial portfolio segment | Commercial and industrial | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	5	0
Commercial portfolio segment | Warehouse
Financing Receivable, Recorded Investment
Loans held-for-investment, net	2,760	1,459
Commercial portfolio segment | Warehouse | Pass
Financing Receivable, Recorded Investment
Loans held-for-investment	2,556	1,324
Commercial portfolio segment | Warehouse | Watch
Financing Receivable, Recorded Investment
Loans held-for-investment	189	120
Commercial portfolio segment | Warehouse | Special Mention
Financing Receivable, Recorded Investment
Loans held-for-investment	15	15
Commercial portfolio segment | Warehouse | Substandard
Financing Receivable, Recorded Investment
Loans held-for-investment	$ 0	$ 0