Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Common stock	Additional paid-in capital	Retained earnings (accumulated deficit)	Accumulated other comprehensive income (loss)	Treasury stock	Noncontrolling interest	Total
Balances at Dec. 31, 2020		$ 4.8	$ 10,321.6	$ 11,838.0	$ 2,383.1	$ (7,988.6)	$ 58.4	$ 16,617.3
Increase (decrease) in stockholders' equity
Common stock issued			42.9					42.9
Stock-based compensation			58.7	(4.5)				54.2
Treasury stock acquired, common						(381.6)		(381.6)
Dividends to common stockholders				(317.4)				(317.4)
Distributions to noncontrolling interest							(3.4)	(3.4)
Contributions from noncontrolling interest							3.8	3.8
Purchase of subsidiary shares from noncontrolling interest			(15.3)				(1.7)	(17.0)
Adjustments to redemption amount of redeemable noncontrolling interest			(8.2)				(0.4)	(8.6)
Net income (loss)				878.9			2.2	881.1
Other comprehensive income (loss)					(579.3)		(0.5)	(579.8)
Balances at Jun. 30, 2021		4.8	10,399.7	12,395.0	1,803.8	(8,370.2)	58.4	16,291.5
Balances at Mar. 31, 2021		4.8	10,351.8	12,199.2	953.8	(8,104.1)	56.8	15,462.3
Increase (decrease) in stockholders' equity
Common stock issued			25.6					25.6
Stock-based compensation			25.0	(2.7)				22.3
Treasury stock acquired, common						(266.1)		(266.1)
Dividends to common stockholders				(165.2)				(165.2)
Distributions to noncontrolling interest							(1.8)	(1.8)
Contributions from noncontrolling interest							2.5	2.5
Purchase of subsidiary shares from noncontrolling interest	[1]		(0.4)					(0.4)
Adjustments to redemption amount of redeemable noncontrolling interest			(2.3)	1.9				(0.4)
Net income (loss)	[1]			361.8			1.2	363.0
Other comprehensive income (loss)	[1]				850.0		(0.3)	849.7
Balances at Jun. 30, 2021		4.8	10,399.7	12,395.0	1,803.8	(8,370.2)	58.4	16,291.5
Balances at Dec. 31, 2021		4.8	10,495.0	12,884.5	1,610.9	(8,925.8)	56.4	16,125.8
Increase (decrease) in stockholders' equity
Common stock issued		0.1	48.9					49.0
Stock-based compensation			56.5	(5.8)			0.2	50.9
Treasury stock acquired, common						(951.3)		(951.3)
Accelerated share repurchase			(42.8)					(42.8)
Dividends to common stockholders				(328.7)				(328.7)
Distributions to noncontrolling interest							(67.0)	(67.0)
Contributions from noncontrolling interest							3.7	3.7
Purchase of subsidiary shares from noncontrolling interest			(4.3)				(2.4)	(6.7)
Adjustments to redemption amount of redeemable noncontrolling interest			0.2				(0.6)	(0.4)
Adjustment for reinsurance					131.8			131.8
Net income (loss)		0.0	0.0	3,435.6	0.0	0.0	53.1	3,488.7
Other comprehensive income (loss)					(7,372.8)		(1.6)	(7,374.4)
Balances at Jun. 30, 2022		4.9	10,553.5	15,985.6	(5,630.1)	(9,877.1)	41.8	11,078.6
Balances at Mar. 31, 2022		4.9	10,402.4	13,090.8	(1,920.6)	(9,679.9)	55.1	11,952.7
Increase (decrease) in stockholders' equity
Common stock issued			29.4					29.4
Stock-based compensation			24.6	(2.9)			0.2	21.9
Treasury stock acquired, common						(197.2)		(197.2)
Accelerated share repurchase			97.2					97.2
Dividends to common stockholders				(161.7)				(161.7)
Distributions to noncontrolling interest							(50.9)	(50.9)
Contributions from noncontrolling interest							2.2	2.2
Adjustments to redemption amount of redeemable noncontrolling interest			(0.1)				(0.2)	(0.3)
Adjustment for reinsurance					131.8			131.8
Net income (loss)	[1]	0.0	0.0	3,059.4	0.0	0.0	38.3	3,097.7
Other comprehensive income (loss)	[1]				(3,841.3)		(2.9)	(3,844.2)
Balances at Jun. 30, 2022		$ 4.9	$ 10,553.5	$ 15,985.6	$ (5,630.1)	$ (9,877.1)	$ 41.8	$ 11,078.6

[1] Excludes amounts attributable to redeemable noncontrolling interest. See Note 11, Stockholders’ Equity, for further details.