Segment Information (Financial Information by Segment) (Details) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)		Jun. 30, 2017 USD ($) reportable_segment	Jun. 30, 2016 USD ($)		Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | reportable_segment					4
Revenues
Net earned premiums		$ 1,115.3	$ 1,202.3		$ 2,165.6	$ 2,617.5
Fees and other income		326.9	328.3		667.1	686.0
Net investment income		121.7	119.8		242.3	255.5
Net realized gains on investments		13.2	21.6	[1]	16.6	183.3	[1]
Amortization of deferred gains and gains on disposal of businesses		23.4	125.8	[2]	60.4	173.4	[2],[3]
Gain on pension plan curtailment		0.0	0.0		0.0	29.6
Total revenues		1,600.5	1,797.8		3,152.0	3,945.3
Benefits, losses and expenses
Policyholder benefits	[4]	416.4	400.8		774.4	944.6
Amortization of deferred acquisition costs and value of business acquired		346.7	342.7		661.2	677.0
Underwriting, general and administrative expenses		646.3	803.6		1,297.6	1,720.9
Interest expense		12.4	15.2		25.0	29.7
Total benefits, losses and expenses		1,421.8	1,562.3		2,758.2	3,372.2
Segment income (loss) before provision (benefit) for income tax		178.7	235.5		393.8	573.1
Provision (benefit) for income taxes		58.5	66.2		129.8	183.4
Net income		120.2	169.3		264.0	389.7
Total assets		30,058.9			30,058.9			$ 29,709.1
Increase (decrease) in premium deficiency reserve liability					796.3	936.8
AEB
Revenues
Net earned premiums	[3]					178.0
Fees and other income	[3]					4.2
Net investment income	[3]					17.3
Net realized gains on investments	[1],[3]					0.0
Amortization of deferred gains and gains on disposal of businesses	[2],[3]					0.0
Gain on pension plan curtailment	[1]					0.0
Total revenues	[1]					199.5
Benefits, losses and expenses
Policyholder benefits	[3],[4]					118.4
Amortization of deferred acquisition costs and value of business acquired	[3]					5.8
Underwriting, general and administrative expenses	[3]					58.5
Interest expense	[3]					0.0
Total benefits, losses and expenses	[3]					182.7
Segment income (loss) before provision (benefit) for income tax	[3]					16.8
Provision (benefit) for income taxes	[3]					6.3
Net income	[3]					10.5
AEB | Disposal group, not discontinued operations
Benefits, losses and expenses
Realized gains on transferred securities supporting retroactive component	[5]	0.0	0.0		0.0	146.7	[6]
Disposal Group, Amortization of Deferred Gain on Disposal	[7]	20.6	122.8		54.8	167.4
Health
Benefits, losses and expenses
Increase (decrease) in premium deficiency reserve liability		(9.2)	(12.2)		(21.9)	1.4
Global Housing
Revenues
Net earned premiums		442.4	451.3		878.8	920.9
Fees and other income		107.8	109.8		203.1	217.6
Net investment income		16.8	17.9		36.0	36.2
Net realized gains on investments		0.0	0.0	[1]	0.0	0.0	[1]
Amortization of deferred gains and gains on disposal of businesses		0.0	0.0	[2]	0.0	0.0	[2],[3]
Gain on pension plan curtailment						0.0
Total revenues		567.0	579.0		1,117.9	1,174.7
Benefits, losses and expenses
Policyholder benefits	[4]	188.2	202.7		351.5	382.2
Amortization of deferred acquisition costs and value of business acquired		46.8	59.7		97.7	119.1
Underwriting, general and administrative expenses		247.5	231.9		488.2	473.3
Interest expense		0.0	0.0		0.0	0.0
Total benefits, losses and expenses		482.5	494.3		937.4	974.6
Segment income (loss) before provision (benefit) for income tax		84.5	84.7		180.5	200.1
Provision (benefit) for income taxes		28.3	27.8		62.4	66.8
Net income		56.2	56.9		118.1	133.3
Total assets		3,744.7			3,744.7
Global Lifestyle
Revenues
Net earned premiums		656.0	739.2		1,251.8	1,462.4
Fees and other income		180.0	175.7		389.1	386.8
Net investment income		26.4	26.3		52.9	53.2
Net realized gains on investments		0.0	0.0	[1]	0.0	0.0	[1]
Amortization of deferred gains and gains on disposal of businesses		0.0	0.0	[2]	0.0	0.0	[2],[3]
Gain on pension plan curtailment						0.0
Total revenues		862.4	941.2		1,693.8	1,902.4
Benefits, losses and expenses
Policyholder benefits	[4]	178.1	161.0		326.7	323.1
Amortization of deferred acquisition costs and value of business acquired		283.6	267.5		534.6	520.5
Underwriting, general and administrative expenses		340.6	464.2		695.3	950.3
Interest expense		0.0	0.0		0.0	0.0
Total benefits, losses and expenses		802.3	892.7		1,556.6	1,793.9
Segment income (loss) before provision (benefit) for income tax		60.1	48.5		137.2	108.5
Provision (benefit) for income taxes		19.9	(1.6)		44.6	17.0
Net income		40.2	50.1		92.6	91.5
Total assets		9,106.9			9,106.9
Global Preneed
Revenues
Net earned premiums		15.2	16.1		29.8	31.8
Fees and other income		31.1	27.2		60.7	54.2
Net investment income		65.0	61.9		129.2	124.0
Net realized gains on investments		0.0	0.0	[1]	0.0	0.0	[1]
Amortization of deferred gains and gains on disposal of businesses		0.0	0.0	[2]	0.0	0.0	[2],[3]
Gain on pension plan curtailment						0.0
Total revenues		111.3	105.2		219.7	210.0
Benefits, losses and expenses
Policyholder benefits	[4]	61.9	61.2		128.1	125.9
Amortization of deferred acquisition costs and value of business acquired		16.3	15.5		28.9	31.6
Underwriting, general and administrative expenses		14.3	11.7		29.2	26.8
Interest expense		0.0	0.0		0.0	0.0
Total benefits, losses and expenses		92.5	88.4		186.2	184.3
Segment income (loss) before provision (benefit) for income tax		18.8	16.8		33.5	25.7
Provision (benefit) for income taxes		6.0	5.5		10.8	8.7
Net income		12.8	11.3		22.7	17.0
Total assets		6,701.8			6,701.8
Total Corporate & Other
Revenues
Net earned premiums		1.7	(4.3)		5.2	24.4
Fees and other income		8.0	15.6		14.2	23.2
Net investment income		13.5	13.7		24.2	24.8
Net realized gains on investments		13.2	21.6	[1]	16.6	183.3	[1]
Amortization of deferred gains and gains on disposal of businesses		23.4	125.8	[2]	60.4	173.4	[2],[3]
Gain on pension plan curtailment						29.6
Total revenues		59.8	172.4		120.6	458.7
Benefits, losses and expenses
Policyholder benefits	[4]	(11.8)	(24.1)		(31.9)	(5.0)
Amortization of deferred acquisition costs and value of business acquired		0.0	0.0		0.0	0.0
Underwriting, general and administrative expenses		43.9	95.8		84.9	212.0
Interest expense		12.4	15.2		25.0	29.7
Total benefits, losses and expenses		44.5	86.9		78.0	236.7
Segment income (loss) before provision (benefit) for income tax		15.3	85.5		42.6	222.0
Provision (benefit) for income taxes		4.3	34.5		12.0	84.6
Net income		11.0	51.0		30.6	137.4
Total assets		10,505.5			10,505.5
Total Corporate & Other | Corporate & Other
Revenues
Net earned premiums		0.0	0.0		0.0	0.0
Fees and other income		6.9	7.3		11.8	9.8
Net investment income		9.8	11.7		19.4	18.9
Net realized gains on investments		13.2	21.6	[1]	16.6	183.3	[1]
Amortization of deferred gains and gains on disposal of businesses		23.4	125.8	[2]	60.4	173.4	[2],[3]
Gain on pension plan curtailment						29.6
Total revenues		53.3	166.4		108.2	415.0
Benefits, losses and expenses
Policyholder benefits	[4]	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		29.9	58.0		57.5	121.3
Interest expense		12.4	15.2		25.0	29.7
Total benefits, losses and expenses		42.3	73.2		82.5	151.0
Segment income (loss) before provision (benefit) for income tax		11.0	93.2		25.7	264.0
Provision (benefit) for income taxes		3.5	36.8		6.5	94.0
Net income		7.5	56.4		19.2	170.0
Total assets		10,364.3			10,364.3
Total Corporate & Other | Health
Revenues
Net earned premiums		1.7	(4.3)		5.2	24.4
Fees and other income		1.1	8.3		2.4	13.4
Net investment income		3.7	2.0		4.8	5.9
Net realized gains on investments		0.0	0.0	[1]	0.0	0.0	[1]
Amortization of deferred gains and gains on disposal of businesses		0.0	0.0	[2]	0.0	0.0	[2],[3]
Gain on pension plan curtailment						0.0
Total revenues		6.5	6.0		12.4	43.7
Benefits, losses and expenses
Policyholder benefits	[4]	(11.8)	(24.1)		(31.9)	(5.0)
Amortization of deferred acquisition costs and value of business acquired		0.0	0.0		0.0	0.0
Underwriting, general and administrative expenses		14.0	37.8		27.4	90.7
Interest expense		0.0	0.0		0.0	0.0
Total benefits, losses and expenses		2.2	13.7		(4.5)	85.7
Segment income (loss) before provision (benefit) for income tax		4.3	(7.7)		16.9	(42.0)
Provision (benefit) for income taxes		0.8	(2.3)		5.5	(9.4)
Net income		3.5	$ (5.4)		11.4	$ (32.6)
Total assets		$ 141.2			$ 141.2

[1] Six months ended June 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 three months ended June 30, 2017 and 2016 include $20.6 and $122.8, respectively, and the six months ended June 30, 2017 and 2016 include $54.8 and $167.4, respectively, related to the amortization of deferred gains and gains related to the AEB sale on March 1, 2016.

[3] AEB amounts represent the results of operations prior to the sale on March 1, 2016.

[4] 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 three months ended June 30, 2017 and 2016, the premium deficiency reserve liability decreased $9.2 and $12.2, respectively. For the six months ended June 30, 2017 and 2016, the premium deficiency reserve liability decreased $21.9 and increased $1.4, respectively. In addition, there was favorable claims development experienced through June 30, 2017, in excess of actual benefit expense, which contributed to the credit balance within policyholder benefits expenses.

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