Stock-Based Compensation (Details) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) shares	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) $ / shares shares	Jun. 30, 2014 USD ($) $ / shares
Stock-based compensation
Aggregate grant-date fair value of stock options, restricted stock awards, performance share awards and restricted stock units | $			$ 19.6
Stock-based compensation expense
Pre-tax compensation expense | $	$ 3.3	$ 3.0	$ 10.5	$ 10.7
Executive Incentive Program
Stock-based compensation
Shares available for grant under the plan	4,201,379		4,201,379
Shares available for issuance under the plan	1,588,163		1,588,163
Nonemployee Director Equity Plan
Stock-based compensation
Shares available for issuance under the plan	245,094		245,094
Stock options
Stock-based compensation
Stock options granted (in shares)			316,345
Portion of stock options vesting on the first anniversary			0.3333
Portion of stock options vesting on the second anniversary			0.3333
Portion of stock options vesting on the third anniversary			0.3333
Maximum term life			10 years
Stock-based compensation expense
Pre-tax compensation expense | $	$ 1.2	$ 1.1	$ 2.5	$ 2.2
Weighted-average assumptions used to estimate grant date fair value of stock options
Expected dividend yield (as a percent)			1.10%	1.20%
Expected life in years			5 years 8 months 16 days	5 years 8 months 27 days
Expected volatility (as a percent)			27.30%	29.30%
Risk-free interest rate (as a percent)			1.40%	1.70%
Weighted average fair value (in dollars per share) | $ / shares			$ 21.19	$ 19.15
Restricted stock awards
Stock-based compensation
Awards granted (in shares)			58,040
Restricted stock awards | Nonemployee Director Equity Plan
Stock-based compensation
Shares available for issuance under the plan	15,094		15,094
Performance share awards
Stock-based compensation
Awards granted (in shares)			58,040
Restricted Stock Units
Stock-based compensation
Awards granted (in shares)			11,471