Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Feb. 20, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Stock-based Compensation arrangements
Stock based compensation expense		$ 8.6	$ 6.3	$ 14.5	$ 9.4
Tax benefits realized for stock-based compensation				5.5	20.4
Supplemental Employee Incentive Plan IV
Stock-based Compensation arrangements
Stock based compensation expense			$ 1.6	$ (0.1)	$ 3.1
Assumptions:
Stock price volatility				30.30%
Risk free rate of return				0.70%
Annual salary increase rate				4.00%
Annual turnover rate				4.60%
Restricted Stock Awards
Stock-based Compensation arrangements
Granted (in shares)				3,400
Granted (in dollars per share)				$ 28.55
Annual forfeiture rate assumption (as a percent)				5.00%
Restricted Stock Units
Stock-based Compensation arrangements
Granted (in shares)				47,320
Granted (in dollars per share)				$ 27.96
Performance Share Awards | Minimum
Stock-based Compensation arrangements
Annual forfeiture rate assumption (as a percent)				0.00%
Performance Share Awards | Maximum
Stock-based Compensation arrangements
Annual forfeiture rate assumption (as a percent)				5.00%
Performance Share Awards Based on Internal Performance Metrics | Maximum
Stock-based Compensation arrangements
Right to receive additional shares, (as a percent)				100.00%
Employee Performance Share Awards
Stock-based Compensation arrangements
Granted (in shares)				349,780
Granted (in dollars per share)				$ 27.71
Number of years over which performance criteria is to be met				3 years
Hybrid Performance Share Awards
Stock-based Compensation arrangements
Granted (in shares)				194,947
Granted (in dollars per share)				$ 27.71
Vesting rights				The 2015 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				$ 100.0
Hybrid Performance Share Awards | Hybrid performance share awards, percentage vesting on each of the first and second anniversary
Stock-based Compensation arrangements
Award vesting rights, percentage		25.00%
Hybrid Performance Share Awards | Hybrid performance share awards, percentage vesting on the third anniversary
Stock-based Compensation arrangements
Award vesting rights, percentage		50.00%
Performance Shares Based on Market Conditions | Maximum
Stock-based Compensation arrangements
Right to receive shares (as a percent)				100.00%
Right to receive an additional award in cash (as a percent)				100.00%
TSR Performance Share Awards
Stock-based Compensation arrangements
Granted (in shares)				292,421
Performance period				3 years
Assumptions:
Fair value per performance share award (in dollars per share)	$ 19.29
Stock price volatility	32.30%
Risk free rate of return	1.00%
Expected dividend yield	0.30%			0.30%
Stock price volatility, minimum				25.60%
Stock price volatility, maximum				29.00%
Risk free rate of return, minimum				0.10%
Risk free rate of return, maximum				0.80%
Fair value per performance share award, minimum (in dollars per share)				$ 14.60
Fair value per performance share award, maximum(in dollars per share)				$ 19.30