Loans Held-for-Investment - Loan Credit Quality Indicators (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Loans held-for-investment
Loans held-for-investment	$ 9,926	$ 9,078
Loans held-for-investment	9,936	9,088
Consumer Loans
Loans held-for-investment
Loans held-for-investment	4,329	4,044
Consumer Loans | Pass
Loans held-for-investment
Loans held-for-investment	4,255	3,971
Consumer Loans | Watch
Loans held-for-investment
Loans held-for-investment	48	51
Consumer Loans | Special Mention
Loans held-for-investment
Loans held-for-investment	0	0
Consumer Loans | Substandard
Loans held-for-investment
Loans held-for-investment	26	22
Residential first mortgage
Loans held-for-investment
Loans held-for-investment	3,092	2,991
Loans held-for-investment	3,100	2,999
Residential first mortgage | Pass
Loans held-for-investment
Loans held-for-investment	3,053	2,952
Residential first mortgage | Watch
Loans held-for-investment
Loans held-for-investment	25	28
Residential first mortgage | Special Mention
Loans held-for-investment
Loans held-for-investment	0	0
Residential first mortgage | Substandard
Loans held-for-investment
Loans held-for-investment	22	19
Home equity
Loans held-for-investment
Loans held-for-investment	794	729
Loans held-for-investment	796	731
Home equity | Pass
Loans held-for-investment
Loans held-for-investment	771	705
Home equity | Watch
Loans held-for-investment
Loans held-for-investment	22	23
Home equity | Special Mention
Loans held-for-investment
Loans held-for-investment	0	0
Home equity | Substandard
Loans held-for-investment
Loans held-for-investment	3	3
Other Consumer
Loans held-for-investment
Loans held-for-investment	433	314
Loans held-for-investment	433	314
Other Consumer | Pass
Loans held-for-investment
Loans held-for-investment	431	314
Other Consumer | Watch
Loans held-for-investment
Loans held-for-investment	1	0
Other Consumer | Special Mention
Loans held-for-investment
Loans held-for-investment	0	0
Other Consumer | Substandard
Loans held-for-investment
Loans held-for-investment	1	0
Commercial Loans
Loans held-for-investment
Loans held-for-investment	5,607	5,044
Commercial Loans | Pass
Loans held-for-investment
Loans held-for-investment	5,250	4,807
Commercial Loans | Watch
Loans held-for-investment
Loans held-for-investment	271	187
Commercial Loans | Special Mention
Loans held-for-investment
Loans held-for-investment	52	49
Commercial Loans | Substandard
Loans held-for-investment
Loans held-for-investment	34	1
Commercial real estate
Loans held-for-investment
Loans held-for-investment	2,324	2,152
Loans held-for-investment	2,324	2,152
Commercial real estate | Pass
Loans held-for-investment
Loans held-for-investment	2,297	2,132
Commercial real estate | Watch
Loans held-for-investment
Loans held-for-investment	20	14
Commercial real estate | Special Mention
Loans held-for-investment
Loans held-for-investment	5	5
Commercial real estate | Substandard
Loans held-for-investment
Loans held-for-investment	2	1
Commercial and industrial
Loans held-for-investment
Loans held-for-investment	1,651	1,433
Loans held-for-investment	1,651	1,433
Commercial and industrial | Pass
Loans held-for-investment
Loans held-for-investment	1,568	1,351
Commercial and industrial | Watch
Loans held-for-investment
Loans held-for-investment	19	53
Commercial and industrial | Special Mention
Loans held-for-investment
Loans held-for-investment	32	29
Commercial and industrial | Substandard
Loans held-for-investment
Loans held-for-investment	32	0
Warehouse lending
Loans held-for-investment
Loans held-for-investment	1,632	1,459
Loans held-for-investment	1,632	1,459
Warehouse lending | Pass
Loans held-for-investment
Loans held-for-investment	1,385	1,324
Warehouse lending | Watch
Loans held-for-investment
Loans held-for-investment	232	120
Warehouse lending | Special Mention
Loans held-for-investment
Loans held-for-investment	15	15
Warehouse lending | Substandard
Loans held-for-investment
Loans held-for-investment	$ 0	$ 0