Stock-based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended							3 Months Ended		9 Months Ended	0 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Supplemental Employee Incentive Plan IV	Sep. 30, 2013 Supplemental Employee Incentive Plan IV	Sep. 30, 2014 Supplemental Employee Incentive Plan IV	Sep. 30, 2013 Supplemental Employee Incentive Plan IV	Aug. 31, 2014 Supplemental Employee Incentive Plans III	Sep. 30, 2014 Restricted Stock Awards	Sep. 30, 2014 Restricted Stock Units	Sep. 30, 2014 Performance Share Awards Minimum	Sep. 30, 2014 Performance Share Awards Maximum	Sep. 30, 2014 Performance Share Awards Based on Internal Performance Metrics Maximum	Sep. 30, 2014 Employee Performance Share Awards	Sep. 30, 2014 Hybrid Performance Share Awards	Sep. 30, 2014 Hybrid Performance Share Awards Hybrid performance share awards, percentage vesting on each of the first and second anniversary	Sep. 30, 2014 Hybrid Performance Share Awards Hybrid performance share awards, percentage vesting on the third anniversary	Sep. 30, 2014 Performance Shares Based on Market Conditions Maximum	Feb. 20, 2014 TSR Performance Share Awards	Sep. 30, 2014 TSR Performance Share Awards Benchmark_Company
Stock-based Compensation arrangements
Stock based compensation expense	$ 5.7	$ 12.2	$ 15.1	$ 41.0	$ 0.2	$ 4.1	$ 3.3	$ 9.2
Tax benefits realized for stock-based compensation			(6.0)	(9.3)
Granted (in shares)										46,000	35,870				241,130	123,257					184,885
Granted (in dollars per share)										$ 34.96	$ 38.73				$ 39.43	$ 39.43
Annual forfeiture rate assumption (as a percent)										5.00%		0.00%	5.00%
Right to receive additional shares (as a percent)														100.00%
Number of years over which performance criteria is to be met															3 years						3 years
Vesting rights																The 2014 awards vest 25% on each of the first and second anniversary dates and 50% on the third anniversary
Minimum operating cash flow for the year preceding the performance period																100
Right to receive shares (as a percent)																			100.00%
Right to receive an additional award in cash (as a percent)																			100.00%
Number of other companies in the Company's peer group																					14
Payments associated with deferred compensation arrangements									$ 13.0
Assumptions:
Fair value per performance share award (in dollars per share)																				$ 32.04
Stock price volatility (as a percent)							33.90%													41.30%
Risk free rate of return (as a percent)							1.00%													0.70%
Expected dividend yield (as a percent)																				0.20%	0.20%
Annual salary increase rate (as a percent)							4.00%
Annual turnover rate							4.60%
Fair value per performance share award Assumptions, low end of range (in dollars per share)																					$ 7.19
Fair value per performance share award Assumptions, high end of range (in dollars per share)																					$ 25.22
Stock Price Volatility, low end of range (as a percent)																					27.50%
Stock Price Volatility, high end of range (as a percent)																					120.40%
Risk free rate of return, low end of range (as a percent)																					0.02%
Risk free rate of return, high end of range (as a percent)																					0.70%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage																	25.00%	50.00%