Other Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loans subject to repurchase from Ginnie Mae	$ 774	$ 266
Goodwill adjustment	55
Goodwill acquired	31
REO loans with government guarantee	10	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	510
Intangible assets acquired	11
Goodwill acquired		29
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]
Intangible assets acquired		103
Goodwill adjustment	$ 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