Income Tax Expense - Valuation Allowance (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Valuation allowance
Valuation allowance	$ 107.3	$ 178.7
Net decrease in U.S. and foreign valuation allowances	71.4	62.5
Estimated cumulative amount of earnings from foreign subsidiaries that are permanently invested	338.3
U.S. Federal
Valuation allowance
Valuation allowance	58.1	126.7
Deferred tax assets | U.S. Federal
Valuation allowance
Valuation allowance	10.4	74.7
Deferred tax assets | State
Valuation allowance
Valuation allowance	36.5	33.8
Tax credit carryforward | Foreign
Valuation allowance
Valuation allowance	11.2	18.2
Net operating loss (NOL) carry forwards | Foreign
Valuation allowance
Valuation allowance	$ 49.2	$ 51.9