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Stockholders' Equity - Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Other Comprehensive Income (Loss)
Other comprehensive income (loss), pre-tax	$ (4,797.5)	$ 1,079.8	$ (9,317.1)	$ (719.3)
Other comprehensive income (loss), tax	952.6	(230.0)	1,942.1	139.6
Other comprehensive income (loss)	(3,844.9)	849.8	(7,375.0)	(579.7)
Net unrealized gains (losses) on available-for-sale securities including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss) before reclassifications, pre-tax	(4,850.9)	1,361.5	(10,393.8)	(1,915.2)
Adjustments for assumed changes in amortization patterns, pre-tax	402.5	(55.5)	747.4	89.1
Adjustments for assumed changes in policyholder liabilities, pre-tax	(123.6)	(318.8)	452.0	1,096.5
Other comprehensive income (loss), pre-tax	(4,523.9)	1,013.4	(9,186.9)	(730.8)
Other comprehensive income (loss) before reclassifications, tax	1,025.3	(273.0)	2,200.4	427.5
Reclassification from accumulated other comprehensive income, tax	(10.6)	(5.7)	(5.4)
Adjustments for assumed changes in amortization patterns, tax	(84.5)	11.7	(156.9)	(18.7)
Adjustments for assumed changes in policyholder liabilities, tax	26.0	44.5	(92.8)	(260.5)
Other comprehensive income (loss), tax	956.2	(222.5)	1,945.3	148.3
Other comprehensive income (loss) before reclassifications, after-tax	(3,825.6)	1,088.5	(8,193.4)	(1,487.7)
Reclassification from accumulated other comprehensive income, after-tax	37.5	20.5	2.1	(1.2)
Adjustments for assumed changes in amortization patterns, after-tax	318.0	(43.8)	590.5	70.4
Adjustments for assumed changes in policyholder liabilities, after-tax	(97.6)	(274.3)	359.2	836.0
Other comprehensive income (loss)	(3,567.7)	790.9	(7,241.6)	(582.5)
Net unrealized gains (losses) on available-for-sale securities including NCI | Net realized capital gains (losses)
Other Comprehensive Income (Loss)
Reclassification from accumulated other comprehensive income, pre-tax	48.1	26.2	7.5	(1.2)
Net unrealized gains (losses) on derivative instruments including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss) before reclassifications, pre-tax	0.6	21.8	(20.4)	22.5
Reclassification from accumulated other comprehensive income, pre-tax	(10.6)	(4.7)	(17.4)	(9.1)
Adjustments for assumed changes in amortization patterns, pre-tax	3.3		5.6
Adjustments for assumed changes in policyholder liabilities, pre-tax	(7.8)	0.4	(2.8)	1.4
Other comprehensive income (loss), pre-tax	(14.5)	17.5	(35.0)	14.8
Other comprehensive income (loss) before reclassifications, tax	(0.1)	(4.6)	4.3	(4.7)
Reclassification from accumulated other comprehensive income, tax	2.2	1.0	3.6	1.9
Adjustments for assumed changes in amortization patterns, tax	(0.7)		(1.2)
Adjustments for assumed changes in policyholder liabilities, tax	1.7		0.6	(0.3)
Other comprehensive income (loss), tax	3.1	(3.6)	7.3	(3.1)
Other comprehensive income (loss) before reclassifications, after-tax	0.5	17.2	(16.1)	17.8
Reclassification from accumulated other comprehensive income, after-tax	(8.4)	(3.7)	(13.8)	(7.2)
Adjustments for assumed changes in amortization patterns, after-tax	2.6		4.4
Adjustments for assumed changes in policyholder liabilities, after-tax	(6.1)	0.4	(2.2)	1.1
Other comprehensive income (loss)	(11.4)	13.9	(27.7)	11.7
Foreign currency translation adjustment including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss), pre-tax	(270.6)	35.9	(115.7)	(20.2)
Other comprehensive income (loss), tax	(3.5)	(0.5)	(5.0)	(0.6)
Other comprehensive income (loss)	(274.1)	35.4	(120.7)	(20.8)
Unrecognized postretirement benefit obligation including NCI
Other Comprehensive Income (Loss)
Other comprehensive income (loss) before reclassifications, pre-tax	2.1		2.1	(9.1)
Other comprehensive income (loss), pre-tax	11.5	13.0	20.5	16.9
Other comprehensive income (loss) before reclassifications, tax	(0.5)		(0.5)	1.9
Reclassification from accumulated other comprehensive income, tax	(2.7)	(3.4)	(5.0)	(6.9)
Other comprehensive income (loss), tax	(3.2)	(3.4)	(5.5)	(5.0)
Other comprehensive income (loss) before reclassifications, after-tax	1.6		1.6	(7.2)
Reclassification from accumulated other comprehensive income, after-tax	6.7	9.6	13.4	19.1
Other comprehensive income (loss)	8.3	9.6	15.0	11.9
Unrecognized postretirement benefit obligation including NCI | Operating expense
Other Comprehensive Income (Loss)
Reclassification from accumulated other comprehensive income, pre-tax	$ 9.4	$ 13.0	$ 18.4	$ 26.0

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