Acquisitions - Acquisition of AMS Group (Details) - USD ($)		3 Months Ended	9 Months Ended	12 Months Ended
	Aug. 01, 2018	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018	Mar. 31, 2019
Business Acquisition [Line Items]
Goodwill acquired			$ 42,000,000
Assurant Mortgage Solutions Group
Business Acquisition [Line Items]
Intangible assets acquired				$ 24,000,000
Goodwill acquired				13,000,000
Xome Holdings LLC | Assurant Mortgage Solutions Group
Business Acquisition [Line Items]
Cash consideration	$ 38,000,000
Contingent consideration		$ 0	0	$ 15,000,000	$ 4,000,000
Estimated consideration	53,000,000
Intangible assets acquired	24,000,000
Goodwill acquired	$ 13,000,000
Change in contingent consideration		$ 4,000,000	$ 15,000,000