Income Taxes - Schedule of componenets of deferred tax assets and liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred Tax Assets
State net operating loss carryforwards	$ 29.3	$ 23.9
Deferred compensation	29.1	23.9
Foreign tax credit carryforwards	0	20.1
Tax benefit of uncertain tax positions	16.2	17.6
Accrued expenses	17.6	6.0
Foreign loss carryforwards	9.1	1.5
Total deferred tax assets	101.3	93.0
Valuation allowance	(36.6)	(21.3)
Deferred tax assets, net of valuation allowance	64.7	71.7
Deferred Tax Liabilities
Intangible asset amortization	(241.3)	(238.2)
Convertible securities interest	(144.7)	(189.2)
Non-deductible intangible amortization	(101.5)	(120.1)
Deferred revenue	(32.1)	(18.5)
Other	(2.0)	(2.8)
Total deferred tax liabilities	(521.6)	(568.8)
Net deferred tax liability	$ (456.9)	$ (497.1)