Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
U.S. federal income taxes (including foreign withholding taxes):
Current federal income taxes																	$ 54.3	$ 117.8	$ 8.0
Deferred federal income taxes																	36.6	46.9	130.7
Total federal income taxes																	90.9	164.7	138.7
State and local income taxes:
Current state and local income taxes																	8.2	15.1	9.7
Deferred state and local income taxes																	(1.5)	13.0	23.8
Total state and local income taxes																	6.7	28.1	33.5
Foreign income taxes:
Current foreign income taxes																	89.8	100.4	115.3
Deferred foreign income taxes																	10.6	(10.4)	(71.0)
Total foreign income taxes																	100.4	90.0	44.3
Total provision for income taxes	$ 106.1		$ 63.8		$ 43.7		$ (15.6)		$ 145.4		$ 61.1		$ 77.7		$ (1.4)		$ 198.0	$ 282.8	$ 216.5

[1] The three months ended March 31, 2016 included tax benefits of $12.2 and $7.5 due to the reversal of valuation allowances and the adoption of FASB ASU 2016-09, respectively. The three months ended June 30 and December 31, 2016 included tax benefits of $23.4 related to the conclusion and settlement of a tax examination of previous years and $37.4 for refunds to be claimed on future amended U.S. federal returns, respectively.