Other Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Feb. 01, 2019	Aug. 01, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans subject to repurchase from Ginnie Mae			$ 629	$ 266
Goodwill			120	23
Goodwill adjustment			55
Goodwill acquired			42
REO loans with government guarantee			8	10
Pacific Union
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans subject to repurchase from Ginnie Mae			418
Goodwill	$ 40				$ 40
Intangible assets acquired			13
Goodwill adjustment	$ 11
Seterus
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Intangible assets acquired			2
Nationstar Mortgage Holdings Inc.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill			65	10		$ 65
Intangible assets acquired				103
Goodwill adjustment		$ 55	$ 55
Goodwill acquired				10
Assurant Mortgage Solutions Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Intangible assets acquired				24
Goodwill acquired				$ 13