Reserves - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Global Housing and Global Lifestyle
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable development	$ 10.8	$ 45.6
Global Housing \| Hurricane Matthew
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable development	13.3	5.2
Assurant Health
Liability for Claims and Claims Adjustment Expense [Line Items]
Favorable development	$ 0.7	$ 8.2

Amount of aggregate reconciling items for the reconciliation of the liability in the disclosure of claims development (in excess of) less than the liability for unpaid claims and claims adjustment expense for short-duration insurance contracts.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671315-158438

Name:	us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimAdjustmentExpenseAggregateReconcilingItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant