Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended			24 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2010
Income Before Income Taxes [Abstract]
Income before income taxes, Domestic	$ 803.3	$ 739.9	$ 629.4
Income before income taxes, International	975.3	1,070.1	1,031.5
Income Before Income Taxes and Income From Equity Method Investments	1,778.6	1,810.0	1,660.9
Income Tax Expense [Abstract]
Income tax expense, current, Federal	342.3	356.1	246.3
Income tax expense, current, State and local	29.9	38.1	30.6
Income tax expense, current, International	324.5	344.8	336.5
Income tax expense, current	696.7	739.0	613.4
Income tax expense, deferred, Federal	(86.7)	(106.4)	0.3
Income tax expense, deferred, State and local	12.1	(2.3)	(3.6)
Income tax expense, deferred, International	(38.5)	(37.2)	(44.9)
Income tax expense, deferred	(113.1)	(145.9)	(48.2)
Income tax expense	$ 583.6	$ 593.1	$ 565.2
Reconciliation from the Statutory U.S. Federal Income Tax Rate to Effective Tax Rate [Abstract]
Statutory U.S. federal income tax rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefit	1.50%	1.30%	1.00%
International tax rate differentials	(3.70%)	(3.30%)	(3.00%)
Other	0.00%	(0.20%)	1.00%
Effective tax rate	32.80%	32.80%	34.00%
Income tax benefit, merger expenses		$ 11.0
Income Tax Expense, Excluding Merger Related Tax Benefit		604.5
Unrecognized Tax Benefits, Penalties and Interest [Abstract]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 1.1	1.7	$ 1.6
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	8.4	14.2
Deferred tax assets:
Compensation and severance	293.8	311.9
Tax loss and credit carryforwards	113.3	95.6
Basis differences from acquisitions	37.1	38.0
Basis differences from short-term assets and liabilities	27.2	27.8
Other	26.9	33.0
Deferred tax assets	498.3	506.3
Valuation allowance	(35.3)	(34.1)
Net deferred tax assets	463.0	472.2
Deferred tax liabilities:
Goodwill and intangible assets	729.5	706.1
Financial instruments	197.3	263.1
Unremitted foreign earnings	9.9	51.1
Basis differences from investments	(4.6)	(4.2)
Deferred tax liabilities	932.1	1,016.1
Long-term deferred tax liabilities	469.1	543.9
Cumulative undistributed earnings of certain foreign subsidiaries indefinitely reinvested	2,100.0
Cumulative undistributed earnings of certain foreign subsidiaries not deemed to be indefinitely reinvested	1,100.0
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
January 1	139.8	137.8
Current year tax positions	5.8	6.0
Prior year tax positions	0.2	1.0
Reduction of prior year tax positions	(25.1)	0.5
Settlements	(6.0)	(0.8)
Lapse of statute of limitations	0.0	(2.9)
Foreign currency translation	(1.7)	(1.8)
December 31	113.0	139.8	137.8
Unrecognized tax benefits that would impact effective tax rate	52.2	58.6
Convertible Debt [Member]
Deferred tax liabilities:
Convertible debt, repayments of convertible debt				$ 1,400.0
Convertible debt, repayments of convertible debt, deferred tax liability				$ 329.0
Taxes paid, cancellation of indebtedness income for debt reacquired	$ 132.0
Convertible Notes due July 31, 2032
Deferred tax liabilities:
Taxes paid, conversion of convertible debt		66.2
Convertible debt, adjustment to additional paid-in capital		32.2
2033 Notes and 2038 Notes [Member]
Deferred tax liabilities:
Taxes paid, conversion of convertible debt		$ 52.7
Convertible debt, adjustment to additional paid-in capital			$ 34.5
Minimum [Member]
Deferred tax liabilities:
Tax loss and credit carryforwards, expiration dates	Dec. 31, 2016
Maximum [Member]
Deferred tax liabilities:
Tax loss and credit carryforwards, expiration dates	Dec. 31, 2035