Accumulated Other Comprehensive Income (Loss) - Details of Changes in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
PRE-TAX
Net Change	$ (2,004.9)	$ (590.2)	$ 790.8
TAX
Net Change	471.3	126.6	(168.1)
AFTER TAX
Net Change	(1,533.6)	(463.6)	622.7
U.S. \| Pension Plans, Defined Benefit
AFTER TAX
Defined benefit plan, net periodic benefit cost (credit), gain (loss) due to settlement	(44.1)	(27.9)	0.0
Unrealized Gains (Losses) on Available for Sale Debt Securities
PRE-TAX
Gains (Losses)	(2,263.8)	(685.0)	706.8
Net Change	(1,984.7)	(721.3)	707.2
TAX
Gains (Losses)	580.2	177.5	(179.3)
Net Change	510.0	186.6	(179.4)
AFTER TAX
Gains (Losses)	(1,683.6)	(507.5)	527.5
Net Change	(1,474.7)	(534.7)	527.8
Interest income on debt securities
PRE-TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	65.1	(36.6)	0.0
TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(16.4)	9.2	0.0
AFTER TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	48.7	(27.4)	0.0
Net gains on debt securities
PRE-TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	214.0	0.3	0.4
TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(53.8)	(0.1)	(0.1)
AFTER TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	160.2	0.2	0.3
Unrealized (Losses) Gains on Cash Flow Hedges
PRE-TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	3.7	(4.5)	(28.1)
Net Change	4.7	1.1	0.8
TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(0.8)	1.1	7.0
Net Change	(1.1)	(0.3)	(0.3)
AFTER TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	2.9	(3.4)	(21.1)
Net Change	3.6	0.8	0.5
Foreign Currency Adjustments
PRE-TAX
Net Change	76.0	53.4	(7.5)
TAX
Net Change	(66.6)	(42.9)	34.4
AFTER TAX
Net Change	9.4	10.5	26.9
Foreign Currency Translation Adjustments
PRE-TAX
Net Change	(200.1)	(133.8)	169.1
TAX
Net Change	3.0	4.1	(8.3)
AFTER TAX
Net Change	(197.1)	(129.7)	160.8
Long-Term Intra-Entity Foreign Currency Transaction (Losses) Gains
PRE-TAX
Net Change	(2.6)	0.6	2.1
TAX
Net Change	0.7	(0.1)	(0.5)
AFTER TAX
Net Change	(1.9)	0.5	1.6
Net Investment Hedge Gains (Losses)
PRE-TAX
Net Change	278.7	186.6	(178.7)
TAX
Net Change	(70.3)	(46.9)	43.2
AFTER TAX
Net Change	208.4	139.7	(135.5)
Pension and Other Postretirement Benefit Adjustments
PRE-TAX
Gains (Losses)	(163.9)	7.9	47.4
Net Change	(100.9)	76.6	90.3
TAX
Gains (Losses)	44.7	0.2	(12.3)
Net Change	29.0	(16.8)	(22.8)
AFTER TAX
Gains (Losses)	(119.2)	8.1	35.1
Net Change	(71.9)	59.8	67.5
Amortization of Net Actuarial Loss
PRE-TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	19.1	41.4	42.2
TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(4.7)	(10.3)	(10.4)
AFTER TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	14.4	31.1	31.8
Amortization of Prior Service Cost (Credit)
PRE-TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(1.0)	(1.0)	(0.1)
TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	0.3	0.3	0.0
AFTER TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(0.7)	(0.7)	(0.1)
Settlement Loss
PRE-TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	44.9	28.3	0.8
TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	(11.3)	(7.0)	(0.1)
AFTER TAX
Reclassification Adjustment for Losses (Gains) Included in Net Income	33.6	21.3	0.7
Foreign Exchange Contracts \| Unrealized (Losses) Gains on Cash Flow Hedges
PRE-TAX
Gains (Losses)	1.0	5.6	28.9
TAX
Gains (Losses)	(0.3)	(1.4)	(7.3)
AFTER TAX
Gains (Losses)	$ 0.7	$ 4.2	$ 21.6

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