Schedule of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance at Beginning of Period	$ (242.5)	$ (276.2)	$ (814.2)	$ 127.5
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (17.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	86.8	(583.8)	666.8	(956.1)
Reclassification from Accumulated Other Comprehensive Income or Loss	2.5	(8.5)	(5.8)	(22.4)
Total Other Comprehensive Income (Loss)	89.3	(592.3)	661.0	(978.5)
Balance at End of Period	(153.2)	(868.5)	(153.2)	(868.5)
Net Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance at Beginning of Period	286.9	224.5	(312.4)	607.8
Cumulative Effect of New Accounting Principle in Period of Adoption					(17.5)
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	118.8	(564.3)	704.8	(930.8)
Reclassification from Accumulated Other Comprehensive Income or Loss	16.4	(0.9)	29.7	(0.2)
Total Other Comprehensive Income (Loss)	135.2	(565.2)	734.5	(931.0)
Balance at End of Period	422.1	(340.7)	422.1	(340.7)
Net Gain on Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance at Beginning of Period	218.0	266.8	250.6	282.3
Cumulative Effect of New Accounting Principle in Period of Adoption					0.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	4.3	(4.8)	0.5	2.9
Reclassification from Accumulated Other Comprehensive Income or Loss	(18.0)	(12.0)	(46.8)	(35.2)
Total Other Comprehensive Income (Loss)	(13.7)	(16.8)	(46.3)	(32.3)
Balance at End of Period	204.3	250.0	204.3	250.0
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance at Beginning of Period	(307.6)	(268.8)	(305.2)	(254.5)
Cumulative Effect of New Accounting Principle in Period of Adoption					0.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	(37.6)	(15.2)	(40.0)	(29.5)
Reclassification from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0	0.0
Total Other Comprehensive Income (Loss)	(37.6)	(15.2)	(40.0)	(29.5)
Balance at End of Period	(345.2)	(284.0)	(345.2)	(284.0)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss), Net of Tax
Balance at Beginning of Period	(439.8)	(498.7)	(447.2)	(508.1)
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 0.0
Other Comprehensive Income (Loss) Before Reclassifications, Net of Tax	1.3	0.5	1.5	1.3
Reclassification from Accumulated Other Comprehensive Income or Loss	4.1	4.4	11.3	13.0
Total Other Comprehensive Income (Loss)	5.4	4.9	12.8	14.3
Balance at End of Period	$ (434.4)	$ (493.8)	$ (434.4)	$ (493.8)