Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 1,001.1	$ 982.8	$ 587.3
Other Comprehensive Income (Loss), before Tax [Abstract]
Currency translation differences on investments in foreign subsidiaries	(364.4)	(121.9)	145.0
Actuarial (loss)/gain related to employee benefit plans	(29.8)	7.0	(4.8)
Prior service credit related to employee benefit plans	23.5	0	0
Reclassification of amortization of prior service costs/(credit) into employee compensation expense	(6.5)	(1.9)	(2.0)
Reclassification of amortization of actuarial (gains)/losses into employee compensation expense	1.8	2.3	2.4
Share of other comprehensive income/(loss) of equity method investments	8.3	(3.9)	6.4
Unrealized (losses)/gains on available-for-sale investments	2.9	13.6	14.0
Reclassification of net (gains)/losses realized on available-for-sale investments included in other gains and losses, net	(12.8)	(3.2)	(3.9)
Other comprehensive income/(loss), before tax	(377.0)	(108.0)	157.1
Other Comprehensive Income (Loss), Tax [Abstract]
Tax benefit/(expense) on foreign currency translation adjustments	0	(0.4)	0.6
Tax on actuarial (loss)/gain related to employee benefit plans	3.8	(5.8)	(0.1)
Prior service credit related to employee benefit plans, Tax	(8.6)	0	0
Reclassification of tax on amortization of prior service costs/(credit) into income tax provision	2.4	0.4	0.5
Reclassification of tax on amortization of actuarial (gains)/losses into income tax provision	(0.4)	(0.5)	(0.6)
Tax on net unrealized (losses)/gains on available-for-sale investments	4.8	(0.5)	(1.0)
Reclassification of tax on net (gains)/losses realized on available-for-sale investments included in income tax provision	(4.1)	(0.9)	(0.2)
Total income tax benefit/(expense) related to items of other comprehensive income	(2.1)	(7.7)	(0.8)
Other comprehensive income/(loss), net of tax	(379.1)	(115.7)	156.3
Total comprehensive income/(loss)	622.0	867.1	743.6
Comprehensive loss/(income) attributable to noncontrolling interests in consolidated entities	(13.0)	(29.4)	90.7
Comprehensive income attributable to common shareholders	$ 609.0	$ 837.7	$ 834.3