Investments in Unconsolidated Affiliates (Financial Information) (Details) - USD ($) $ in Millions	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments in and Advances to Affiliates
Total investments	$ 4,280.7				$ 3,742.4					$ 4,280.7	$ 3,742.4
Total assets	10,284.5				10,455.7					10,284.5	10,455.7
Long-term debt	442.4				343.1					442.4	343.1
Total liabilities	5,916.5				5,917.3					5,916.5	5,917.3
Common shareholders’ equity	4,368.0				4,538.4					4,368.0	4,538.4
Earned insurance premiums										1,188.2	1,185.0	$ 1,120.9
Net investment income										60.8	59.5	59.8
Revenues (including realized gains and losses)	678.5	$ 334.7	$ 403.6	$ 391.8	405.6	$ 323.2	$ 393.5	$ 331.8		1,808.6	1,454.1	1,361.6
Expenses	$ 420.4	429.3	$ 412.7	$ 391.3	471.3	$ 358.7	$ 359.9	$ 293.2		1,653.7	1,483.1	1,203.0
Net income										279.5	290.0	309.1
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest										$ 197.2	207.3	247.0
Symetra
Investments in and Advances to Affiliates
Total investments		32,409.2			30,634.3				$ 32,409.2		30,634.3
Separate account assets		885.9			949.8				885.9		949.8
Total assets		34,962.8			33,001.7				34,962.8		33,001.7
Policyholder liabilities		29,492.0			27,276.0				29,492.0		27,276.0
Long-term debt		697.5			697.2				697.5		697.2
Separate account liabilities		885.9			949.8				885.9		949.8
Total liabilities		31,836.7			29,641.1				31,836.7		29,641.1
Common shareholders’ equity		$ 3,126.1			$ 3,360.6				3,126.1		3,360.6
Earned insurance premiums									539.3		629.1	627.2
Net investment income									994.3		1,320.5	1,285.0
Revenues (including realized gains and losses)									1,605.9		2,182.4	2,139.5
Liability for Future Policy Benefits, Period Expense (Income)									1,143.7		1,399.7	1,394.9
Expenses									1,543.6		1,882.5	1,865.4
Net income									89.6		254.4	220.7
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest									$ (234.1)		$ 397.0	$ (777.6)