Income Taxes (Current and Deferred) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal									$ (100.6)	$ (57.0)	$ 660.5
Foreign									38.5	378.9	422.0
State									4.0	(125.0)	47.5
2017 Tax Act - provisional									3,247.5	0.0	0.0
Total current tax expense									3,189.4	196.9	1,130.0
Deferred:
Federal									801.5	517.0	(689.6)
Foreign									(256.3)	(83.3)	(66.0)
State									0.4	5.8	7.2
2017 Tax Act - provisional									(1,333.5)	0.0	0.0
Total deferred tax (benefit) expense									(787.9)	439.5	(748.4)
Income taxes	$ 1,941.0	$ 36.0	$ 252.5	$ 172.0	$ 120.2	$ 192.7	$ 196.8	$ 126.7	$ 2,401.5	$ 636.4	$ 381.6