Segment Information (Financial Information By Segment) (Details) $ in Millions		3 Months Ended								12 Months Ended
	Dec. 22, 2017 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) reportable_segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | reportable_segment										4
Revenues
Net earned premiums										$ 4,404.1	$ 5,007.3	$ 8,351.0
Fees and other income										1,383.1	1,422.5	1,303.5
Net investment income										493.8	515.7	626.2
Net realized gains on investments										30.1	162.2	31.8
Amortization of deferred gains and gains on disposal of businesses										103.9	394.5	13.0
Gain on pension plan curtailment									$ 29.6	0.0	29.6	0.0
Total revenues		$ 1,676.6	$ 1,586.4	$ 1,600.5	$ 1,551.5	$ 1,752.4	$ 1,834.1	$ 1,797.8	2,147.5	6,415.0	7,531.8	10,325.5
Benefits, losses and expenses
Policyholder benefits										1,870.6	1,808.5	4,742.5
Amortization of deferred acquisition costs and value of business acquired										1,340.0	1,351.3	1,402.6
Underwriting, general and administrative expenses										2,710.4	3,442.8	3,924.1
Interest expense										49.5	57.6	55.1
Loss on extinguishment of debt										0.0	23.0	0.0
Total benefits, losses and expenses										5,970.5	6,683.2	10,124.3
Income before (benefit) provision for income taxes		158.3	(107.6)	178.7	215.1	54.6	220.9	235.5	337.6	444.5	848.6	201.2
Provision (benefit) for income taxes										(75.1)	283.2	59.6
Net income		312.9	$ (57.3)	$ 120.2	$ 143.8	31.3	$ 144.4	$ 169.3	$ 220.4	519.6	565.4	141.6
Total assets		31,843.0				29,709.1				31,843.0	29,709.1
Restructuring Charges										3.3	31.4	85.6
One time tax benefit	$ 177.0	177.0
Corporate & Other
Benefits, losses and expenses
Intangible asset impairment charge											16.7
Post-close adjustment for estimated indemnification										17.4	23.0
Health
Benefits, losses and expenses
Restructuring Charges										35.7	37.6	44.5
Global Housing
Revenues
Net earned premiums										1,761.4	1,829.1	2,044.7
Fees and other income										413.6	459.7	405.5
Net investment income										75.6	72.7	92.8
Net realized gains on investments										0.0	0.0	0.0
Amortization of deferred gains and gains on disposal of businesses										0.0	0.0	0.0
Gain on pension plan curtailment											0.0
Total revenues										2,250.6	2,361.5	2,543.0
Benefits, losses and expenses
Policyholder benefits										958.4	828.6	788.5
Amortization of deferred acquisition costs and value of business acquired										194.9	238.2	280.4
Underwriting, general and administrative expenses										953.0	1,013.7	1,010.5
Interest expense										0.0	0.0	0.0
Loss on extinguishment of debt											0.0
Total benefits, losses and expenses										2,106.3	2,080.5	2,079.4
Income before (benefit) provision for income taxes										144.3	281.0	463.6
Provision (benefit) for income taxes										46.9	92.4	155.9
Net income										97.4	188.6	307.7
Total assets		4,809.6				3,836.5				4,809.6	3,836.5
Global Lifestyle
Revenues
Net earned premiums										2,576.5	2,901.4	2,955.4
Fees and other income										819.7	804.7	678.6
Net investment income										114.6	113.1	126.9
Net realized gains on investments										0.0	0.0	0.0
Amortization of deferred gains and gains on disposal of businesses										0.0	0.0
Gain on pension plan curtailment											0.0
Total revenues										3,510.8	3,819.2	3,760.9
Benefits, losses and expenses
Policyholder benefits										700.4	663.8	679.8
Amortization of deferred acquisition costs and value of business acquired										1,083.3	1,045.9	1,022.0
Underwriting, general and administrative expenses										1,480.8	1,901.8	1,847.8
Interest expense										0.0	0.0	0.0
Loss on extinguishment of debt											0.0
Total benefits, losses and expenses										3,264.5	3,611.5	3,549.6
Income before (benefit) provision for income taxes										246.3	207.7	211.3
Provision (benefit) for income taxes										68.3	53.3	58.3
Net income										178.0	154.4	153.0
Total assets		9,497.6				8,747.0				9,497.6	8,747.0
Global Preneed
Revenues
Net earned premiums										59.5	61.7	60.4
Fees and other income										121.5	109.6	107.1
Net investment income										262.0	259.8	249.8
Net realized gains on investments										0.0	0.0	0.0
Amortization of deferred gains and gains on disposal of businesses										0.0	0.0	0.0
Gain on pension plan curtailment											0.0
Total revenues										443.0	431.1	417.3
Benefits, losses and expenses
Policyholder benefits										259.1	250.4	239.7
Amortization of deferred acquisition costs and value of business acquired										61.8	61.4	56.6
Underwriting, general and administrative expenses										63.1	55.5	55.9
Interest expense										0.0	0.0	0.0
Loss on extinguishment of debt											0.0
Total benefits, losses and expenses										384.0	367.3	352.2
Income before (benefit) provision for income taxes										59.0	63.8	65.1
Provision (benefit) for income taxes										19.4	21.5	20.9
Net income										39.6	42.3	44.2
Total assets		6,827.1				6,421.1				6,827.1	6,421.1
Total Corporate & Other
Revenues
Net earned premiums										6.7	37.1	2,223.7
Fees and other income										28.3	44.3	87.3
Net investment income										41.6	52.8	45.7
Net realized gains on investments										30.1	162.2	31.8
Amortization of deferred gains and gains on disposal of businesses										103.9	394.5	13.0
Gain on pension plan curtailment											29.6
Total revenues										210.6	720.5	2,401.5
Benefits, losses and expenses
Policyholder benefits										(47.3)	(52.7)	2,304.3
Amortization of deferred acquisition costs and value of business acquired										0.0	0.0	10.7
Underwriting, general and administrative expenses										213.5	410.3	644.0
Interest expense										49.5	57.6	55.1
Loss on extinguishment of debt											23.0
Total benefits, losses and expenses										215.7	438.2	3,014.1
Income before (benefit) provision for income taxes										(5.1)	282.3	(612.6)
Provision (benefit) for income taxes										(209.7)	110.7	(202.0)
Net income										204.6	171.6	(410.6)
Total assets		10,708.7				10,704.5				10,708.7	10,704.5
Total Corporate & Other | Corporate & Other
Revenues
Net earned premiums										0.0	0.0	0.0
Fees and other income										24.8	24.5	32.7
Net investment income										35.1	44.0	21.2
Net realized gains on investments										30.1	162.2	31.8
Amortization of deferred gains and gains on disposal of businesses										103.9	394.5	13.0
Gain on pension plan curtailment											29.6
Total revenues										193.9	654.8	98.7
Benefits, losses and expenses
Policyholder benefits										0.0	0.0	3.1
Amortization of deferred acquisition costs and value of business acquired										0.0	0.0	0.0
Underwriting, general and administrative expenses										165.5	244.6	127.3
Interest expense										49.5	57.6	55.1
Loss on extinguishment of debt											23.0
Total benefits, losses and expenses										215.0	325.2	185.5
Income before (benefit) provision for income taxes										(21.1)	329.6	(86.8)
Provision (benefit) for income taxes										(215.1)	117.0	(44.1)
Net income										194.0	212.6	(42.7)
Total assets		10,633.6				10,457.8				10,633.6	10,457.8
Total Corporate & Other | Health
Revenues
Net earned premiums										6.7	37.1	2,223.7
Fees and other income										3.5	19.8	54.6
Net investment income										6.5	8.8	24.5
Net realized gains on investments										0.0	0.0	0.0
Amortization of deferred gains and gains on disposal of businesses										0.0	0.0	0.0
Gain on pension plan curtailment											0.0
Total revenues										16.7	65.7	2,302.8
Benefits, losses and expenses
Policyholder benefits										(47.3)	(52.7)	2,301.2
Amortization of deferred acquisition costs and value of business acquired										0.0	0.0	10.7
Underwriting, general and administrative expenses										48.0	165.7	516.7
Interest expense										0.0	0.0	0.0
Loss on extinguishment of debt											0.0
Total benefits, losses and expenses										0.7	113.0	2,828.6
Income before (benefit) provision for income taxes										16.0	(47.3)	(525.8)
Provision (benefit) for income taxes										5.4	(6.3)	(157.9)
Net income										10.6	(41.0)	(367.9)
Total assets		$ 75.1				246.7				75.1	246.7
Employee Benefits
Revenues
Net earned premiums											178.0	1,066.8
Fees and other income											4.2	25.0
Net investment income											17.3	111.0
Net realized gains on investments											0.0	0.0
Amortization of deferred gains and gains on disposal of businesses											0.0	0.0
Gain on pension plan curtailment											0.0
Total revenues											199.5	1,202.8
Benefits, losses and expenses
Policyholder benefits											118.4	730.2
Amortization of deferred acquisition costs and value of business acquired											5.8	32.9
Underwriting, general and administrative expenses											61.5	365.9
Interest expense											0.0	0.0
Loss on extinguishment of debt											0.0
Total benefits, losses and expenses											185.7	1,129.0
Income before (benefit) provision for income taxes											13.8	73.8
Provision (benefit) for income taxes											5.3	26.5
Net income											8.5	$ 47.3
Total assets						$ 0.0					0.0
Disposal group, disposed of by sale, not discontinued operations | Employee Benefits
Benefits, losses and expenses
Amortization of deferred gains										92.8	382.6
Realized gains on transferred securities supporting retroactive component										$ 0.0	$ 146.7