Dispositions (Narrative) (Details) - USD ($) $ in Thousands			3 Months Ended					9 Months Ended			24 Months Ended
		Mar. 01, 2016	Dec. 31, 2016	Sep. 30, 2016		Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2016		Sep. 30, 2015	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash consideration from disposal	[1]							$ 873,920		$ 65,002
Disposal Group, Not Discontinued Operations | Employee Benefits Segment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash consideration from disposal		$ 926,174
Consideration from disposal consisting of account renewals	[2]	16,000
Estimated gain disposal before adjustment		638,517
Estimated gain (loss) on disposal		656,497				$ 640,497
Gain (loss) net of tax		120,077
Deferred gain on disposal, before adjustment		518,440
Amortization of deferred gains	[2]			$ 116,856		$ 122,835	$ 44,593	284,284
Gain (loss) on disposal								420,361
Deferred gain on disposal		$ 520,420		$ 236,136	[3]			236,136	[3]
Pretax income from disposal								$ 16,747		$ 49,754
Scenario, Forecast | Disposal Group, Not Discontinued Operations | Employee Benefits Segment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent of deferred gain to be earned (over)			70.00%								90.00%

[1] Relates to the sale of Assurant's Employee Benefits segment mainly through reinsurance transactions and supplemental and small group self-funded business.

[2] Amount classified as amortization of deferred gains and gains on disposal of businesses within the Consolidated Statements of Operations.

[3] Amount classified as a component of the deferred gains on disposal of businesses within the Consolidated Balance Sheets.