Consolidated Statements of Stockholders' Equity (USD $) In Millions, unless otherwise specified	Total	Common stock	Additional paid-in capital	Retained earnings (deficit)	Accumulated other comprehensive income (loss)	Treasury stock	Noncontrolling interest	Comprehensive income (loss)	Series A Preferred stock	Series B Preferred stock
Balances at Dec. 31, 2008	$ 2,569.3	$ 3.9	$ 8,376.5	$ 3,722.5	$ (4,911.6)	$ (4,718.6)	$ 96.5			$ 0.1
Increase (decrease) in stockholders' equity
Common stock issued	1,123.0	0.6	1,122.4
Stock-based compensation and additional related tax benefits	38.0		39.9	(1.9)
Treasury stock acquired, common	(4.1)					(4.1)
Dividends to common stockholders	(159.5)			(159.5)
Dividends to preferred stockholders	(33.0)			(33.0)
Distributions to noncontrolling interest	(7.1)						(7.1)
Contributions from noncontrolling interest	10.1						10.1
Purchase of subsidiary shares from noncontrolling interest	(45.7)		(45.9)				0.2
Effects of reclassifying noncredit component of previously recognized impairment losses on fixed maturities, available-for-sale, net				9.9	(9.9)
Comprehensive income (loss):
Net income (loss)	645.7			622.7			23.0	645.7
Net unrealized gains (losses), net	3,693.1				3,693.1			3,693.1
Noncredit component of impairment losses on fixed maturities, available-for-sale, net	(152.9)				(152.9)			(152.9)
Foreign currency translation adjustment, net of related income taxes	168.4				168.2		0.2	168.4
Unrecognized postretirement benefit obligation, net of related income taxes	171.1				171.1			171.1
Comprehensive income (loss)	4,525.4							4,525.4
Balances at Dec. 31, 2009	8,016.4	4.5	9,492.9	4,160.7	(1,042.0)	(4,722.7)	122.9			0.1
Increase (decrease) in stockholders' equity
Common stock issued	20.6		20.6
Stock-based compensation and additional related tax benefits	47.9		50.3	(2.4)
Treasury stock acquired, common	(2.6)					(2.6)
Dividends to common stockholders	(176.2)			(176.2)
Dividends to preferred stockholders	(33.0)			(33.0)
Distributions to noncontrolling interest	(7.8)						(7.8)
Contributions from noncontrolling interest	24.0						24.0
Effects of implementation of accounting change related to variable interest entities, net				(10.7)	10.7
Effects of electing fair value option for fixed maturities upon implementation of accounting change related to embedded credit derivatives, net				(25.4)	25.4
Comprehensive income (loss):
Net income (loss)	717.2			699.3			17.9	717.2
Net unrealized gains (losses), net	1,070.6				1,070.6			1,070.6
Noncredit component of impairment losses on fixed maturities, available-for-sale, net	(33.5)				(33.5)			(33.5)
Foreign currency translation adjustment, net of related income taxes	33.4				33.2		0.2	33.4
Unrecognized postretirement benefit obligation, net of related income taxes	208.0				208.0			208.0
Comprehensive income (loss)	1,995.7							1,995.7
Balances at Dec. 31, 2010	9,885.0	4.5	9,563.8	4,612.3	272.4	(4,725.3)	157.2			0.1
Increase (decrease) in stockholders' equity
Common stock issued	25.9		25.9
Stock-based compensation and additional related tax benefits	43.9		47.0	(3.1)
Treasury stock acquired, common	(556.4)					(556.4)
Dividends to common stockholders	(213.7)			(213.7)
Dividends to preferred stockholders	(33.0)			(33.0)
Distributions to noncontrolling interest	(9.8)						(9.8)
Contributions from noncontrolling interest	196.7						196.7
Purchase of subsidiary shares from noncontrolling interest	(5.7)		(2.0)				(3.7)
Comprehensive income (loss):
Net income (loss)	751.2			715.0			36.2	751.2
Net unrealized gains (losses), net	213.7				213.7			213.7
Noncredit component of impairment losses on fixed maturities, available-for-sale, net	31.4				31.4			31.4
Foreign currency translation adjustment, net of related income taxes	(143.3)				(142.7)		(0.6)	(143.3)
Unrecognized postretirement benefit obligation, net of related income taxes	(172.9)				(172.9)			(172.9)
Comprehensive income (loss)	680.1							680.1
Balances at Dec. 31, 2011	$ 10,013.0	$ 4.5	$ 9,634.7	$ 5,077.5	$ 201.9	$ (5,281.7)	$ 376.0		$ 0	$ 0.1