Segment Information (Financial Information by Segment) (Details) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)		Sep. 30, 2017 USD ($) reportable_segment		Sep. 30, 2016 USD ($)		Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | reportable_segment					4
Revenues
Net earned premiums		$ 1,073.1	$ 1,215.1		$ 3,238.7		$ 3,832.6
Fees and other income		349.1	347.7		1,016.2		1,033.7
Net investment income		132.6	124.8		374.9		380.3
Net realized gains on investments		8.5	10.7		25.1		194.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	23.1	135.8		83.5		309.2
Gain on pension plan curtailment		0.0	0.0		0.0		29.6
Total revenues		1,586.4	1,834.1		4,738.4		5,779.4
Benefits, losses and expenses
Policyholder benefits	[3]	682.2	435.2		1,456.6		1,379.8
Amortization of deferred acquisition costs and value of business acquired		332.5	330.3		993.7		1,007.3
Underwriting, general and administrative expenses		667.1	833.7		1,964.7		2,554.6
Interest expense		12.2	14.0		37.2		43.7
Total benefits, losses and expenses		1,694.0	1,613.2		4,452.2		4,985.4
Segment income (loss) before provision (benefit) for income tax		(107.6)	220.9		286.2		794.0
Provision (benefit) for income taxes		(50.3)	76.5		79.5		259.9
Net (loss) income		(57.3)	144.4		206.7		534.1
Increase (decrease) in premium deficiency reserve liability					1,485.1		1,395.0
Total assets		32,405.2			32,405.2				$ 29,709.1
AEB
Revenues
Net earned premiums							178.0
Fees and other income							4.2
Net investment income							17.3
Net realized gains on investments	[1]						0.0
Amortization of deferred gains and gains on disposal of businesses							0.0
Gain on pension plan curtailment							0.0
Total revenues							199.5
Benefits, losses and expenses
Policyholder benefits	[3]						118.4
Amortization of deferred acquisition costs and value of business acquired							5.8
Underwriting, general and administrative expenses							58.5
Interest expense							0.0
Total benefits, losses and expenses							182.7
Segment income (loss) before provision (benefit) for income tax							16.8
Provision (benefit) for income taxes							6.3
Net (loss) income							10.5
AEB | Disposal group, not discontinued operations
Benefits, losses and expenses
Amortization of deferred gains	[4]	20.4	132.9		75.2		300.4
Realized gain on contingent consideration							16.0
Realized gains on transferred securities supporting retroactive component	[5]	0.0	0.0		0.0		146.7	[6]
Corporate & Other
Benefits, losses and expenses
Post-close adjustment for estimated indemnification		4.5	18.0		6.0		18.0
Health
Benefits, losses and expenses
Increase (decrease) in premium deficiency reserve liability		(6.9)	(21.6)		(28.8)		(20.2)
Global Housing
Revenues
Net earned premiums		423.0	457.4		1,301.8		1,378.3
Fees and other income		107.3	121.6		310.4		339.2
Net investment income		23.6	17.0		59.6		53.2
Net realized gains on investments		0.0	0.0		0.0		0.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	0.0	0.0		0.0		0.0
Gain on pension plan curtailment							0.0
Total revenues		553.9	596.0		1,671.8		1,770.7
Benefits, losses and expenses
Policyholder benefits	[3]	436.7	218.6		788.2		600.8
Amortization of deferred acquisition costs and value of business acquired		49.7	52.1		147.4		171.2
Underwriting, general and administrative expenses		235.0	260.7		723.2		734.0
Interest expense		0.0	0.0		0.0		0.0
Total benefits, losses and expenses		721.4	531.4		1,658.8		1,506.0
Segment income (loss) before provision (benefit) for income tax		(167.5)	64.6		13.0		264.7
Provision (benefit) for income taxes		(57.2)	20.1		5.2		86.9
Net (loss) income		(110.3)	44.5		7.8		177.8
Total assets		5,609.1			5,609.1
Global Lifestyle
Revenues
Net earned premiums		636.0	742.0		1,887.8		2,204.4
Fees and other income		205.7	185.8		594.8		572.6
Net investment income		33.1	27.4		86.0		80.6
Net realized gains on investments		0.0	0.0		0.0		0.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	0.0	0.0		0.0		0.0
Gain on pension plan curtailment							0.0
Total revenues		874.8	955.2		2,568.6		2,857.6
Benefits, losses and expenses
Policyholder benefits	[3]	190.6	180.1		517.3		503.2
Amortization of deferred acquisition costs and value of business acquired		266.1	263.0		800.7		783.5
Underwriting, general and administrative expenses		371.9	470.0		1,067.2		1,420.3
Interest expense		0.0	0.0		0.0		0.0
Total benefits, losses and expenses		828.6	913.1		2,385.2		2,707.0
Segment income (loss) before provision (benefit) for income tax		46.2	42.1		183.4		150.6
Provision (benefit) for income taxes		3.6	13.8		48.2		30.8
Net (loss) income		42.6	28.3		135.2		119.8
Total assets		9,447.8			9,447.8
Global Preneed
Revenues
Net earned premiums		14.0	15.2		43.8		47.0
Fees and other income		30.6	28.0		91.3		82.2
Net investment income		66.4	68.0		195.6		192.0
Net realized gains on investments		0.0	0.0		0.0		0.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	0.0	0.0		0.0		0.0
Gain on pension plan curtailment							0.0
Total revenues		111.0	111.2		330.7		321.2
Benefits, losses and expenses
Policyholder benefits	[3]	62.6	60.9		190.7		186.8
Amortization of deferred acquisition costs and value of business acquired		16.7	15.2		45.6		46.8
Underwriting, general and administrative expenses		13.3	14.3		42.5		41.1
Interest expense		0.0	0.0		0.0		0.0
Total benefits, losses and expenses		92.6	90.4		278.8		274.7
Segment income (loss) before provision (benefit) for income tax		18.4	20.8		51.9		46.5
Provision (benefit) for income taxes		6.1	6.4		16.9		15.1
Net (loss) income		12.3	14.4		35.0		31.4
Total assets		6,897.9			6,897.9
Total Corporate & Other
Revenues
Net earned premiums		0.1	0.5		5.3		24.9
Fees and other income		5.5	12.3		19.7		35.5
Net investment income		9.5	12.4		33.7		37.2
Net realized gains on investments		8.5	10.7		25.1		194.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	23.1	135.8		83.5		309.2
Gain on pension plan curtailment							29.6
Total revenues		46.7	171.7		167.3		630.4
Benefits, losses and expenses
Policyholder benefits	[3]	(7.7)	(24.4)		(39.6)		(29.4)
Amortization of deferred acquisition costs and value of business acquired		0.0	0.0		0.0		0.0
Underwriting, general and administrative expenses		46.9	88.7		131.8		300.7
Interest expense		12.2	14.0		37.2		43.7
Total benefits, losses and expenses		51.4	78.3		129.4		315.0
Segment income (loss) before provision (benefit) for income tax		(4.7)	93.4		37.9		315.4
Provision (benefit) for income taxes		(2.8)	36.2		9.2		120.8
Net (loss) income		(1.9)	57.2		28.7		194.6
Total assets		10,450.4			10,450.4
Total Corporate & Other | Corporate & Other
Revenues
Net earned premiums		0.0	0.0		0.0		0.0
Fees and other income		4.5	7.3		16.3		17.1
Net investment income		8.6	10.8		28.0		29.7
Net realized gains on investments		8.5	10.7		25.1		194.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	23.1	135.8		83.5		309.2
Gain on pension plan curtailment							29.6
Total revenues		44.7	164.6		152.9		579.6
Benefits, losses and expenses
Policyholder benefits	[3]	0.0	0.0		0.0		0.0
Amortization of deferred acquisition costs and value of business acquired		0.0	0.0		0.0		0.0
Underwriting, general and administrative expenses		38.2	57.2	[7]	95.7	[7]	178.5	[7]
Interest expense		12.2	14.0		37.2		43.7
Total benefits, losses and expenses		50.4	71.2		132.9		222.2
Segment income (loss) before provision (benefit) for income tax		(5.7)	93.4		20.0		357.4
Provision (benefit) for income taxes		(3.7)	34.5		2.8		128.5
Net (loss) income		(2.0)	58.9		17.2		228.9
Total assets		10,325.9			10,325.9
Total Corporate & Other | Health
Revenues
Net earned premiums		0.1	0.5		5.3		24.9
Fees and other income		1.0	5.0		3.4		18.4
Net investment income		0.9	1.6		5.7		7.5
Net realized gains on investments		0.0	0.0		0.0		0.0	[1]
Amortization of deferred gains and gains on disposal of businesses	[2]	0.0	0.0		0.0		0.0
Gain on pension plan curtailment							0.0
Total revenues		2.0	7.1		14.4		50.8
Benefits, losses and expenses
Policyholder benefits	[3]	(7.7)	(24.4)		(39.6)		(29.4)
Amortization of deferred acquisition costs and value of business acquired		0.0	0.0		0.0		0.0
Underwriting, general and administrative expenses		8.7	31.5		36.1		122.2
Interest expense		0.0	0.0		0.0		0.0
Total benefits, losses and expenses		1.0	7.1		(3.5)		92.8
Segment income (loss) before provision (benefit) for income tax		1.0	0.0		17.9		(42.0)
Provision (benefit) for income taxes		0.9	1.7		6.4		(7.7)
Net (loss) income		0.1	$ (1.7)		11.5		(34.3)
Total assets		$ 124.5			$ 124.5
Trade Names | Corporate & Other
Benefits, losses and expenses
Asset Impairment Charges							$ 16.7

[1] Nine months ended September 30, 2016 includes $146.7 of net realized gains related to assets transferred to Sun Life as part of the AEB sale on March 1, 2016.

[2] The nine months ended September 30, 2017 and 2016 include $75.2 and $300.4, respectively, related to the amortization of deferred gains and gains related to the AEB sale on March 1, 2016.

[3] The presentation of Assurant Health policyholder benefits includes the impact of the total current period net utilization of premium deficiency reserves for claim costs and claim adjustment expenses included in policyholder benefits, as well as maintenance costs, which are included within underwriting, general and administrative expenses. For the nine months ended September 30, 2017 and 2016, the premium deficiency reserve liability decreased $28.8 and $20.2, respectively, through an offset to policyholder benefit expense. In addition, there was favorable claims development experienced through September 30, 2017, in excess of actual benefit expense, which contributed to the credit balance within policyholder benefits expenses.

[4] Amount classified as amortization of deferred gains and gains on disposal of businesses within the consolidated statements of operations. The nine months ended September 30, 2017 amount includes subsequent novations of $1.4 that allowed immediate gain recognition.

[5] Reinsurance of existing claims liabilities requires retroactive accounting necessitating losses to be recognized immediately. However, upon transfer of the associated assets supporting the liabilities, the Company recognized realized gains which more than offset the retroactive losses. The Company was required to classify the realized gains as part of net realized gains on investments, within the consolidated statements of operations.

[6] Amount classified within underwriting, general and administrative expenses in the consolidated statements of operations.

[7] The nine months ended September 30, 2016 for Corporate and Other includes a $16.7 intangible asset impairment charge related to trade names that will no longer be used or defended by the Company, and the nine months ended September 30, 2017 and 2016, for Corporate and Other includes expense of $6.0 and $18.0, respectively, related to post-close adjustment pertaining to an estimated indemnification that is expected to be due on a previous disposition.