Stock Compensation Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2004
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 1.9	$ 1.4
Income tax benefit	(0.7)	(0.5)
Stock-based compensation, net of income tax benefit	1.2	0.9
Compensation costs related to equity awards and amounts recognized
Compensation expense recognized	(1.9)	(1.4)
Outstanding stock options and SARs
Excess tax benefits (deficiency) related to the exercise or vesting of stock-based awards	0.5	1.9
Options
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	0.9
Compensation costs related to equity awards and amounts recognized
Unrecognized compensation cost at the beginning of the period	1.1
Grant date fair value of current year grants	1.4
Compensation expense recognized	(0.9)
Unrecognized compensation cost at the end of the period	1.6
Expected amortization period	2 years 2 months 12 days
Fair value assumptions
Expected term in years	5 years 9 months 18 days
Risk free interest rate (as a percent)	1.40%
Volatility (as a percent)	34.40%
Dividend yield (as a percent)	2.00%
Additional disclosures
Aggregate pre-tax intrinsic value of stock options and SARs exercised	2.0	6.9
Outstanding stock options and SARs
Stock options and SARs vested or expected to vest (in shares)	619,500		601,100
Aggregate intrinsic value (in dollars)	19.7		20.3
Per share weighted average grant date fair value (in dollars per share)	$ 30.78		$ 26.46
Exercisable stock options and SARs (in shares)	314,600		292,900
Aggregate intrinsic value (in dollars)	12.4		11.4
Unvested stock options and SARs (in shares)	309,500		311,100
Per share weighted average grant date fair value (in dollars per share)	$ 12.17		$ 10.37
Performance Shares and Restricted Stock
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	1.0
Compensation costs related to equity awards and amounts recognized
Unrecognized compensation cost at the beginning of the period	2.2
Grant date fair value of current year grants	2.1
Compensation expense recognized	(1.0)
Unrecognized compensation cost at the end of the period	3.3
Expected amortization period	2 years 2 months 12 days
Nonqualified stock options
Stock options awarded
Nonqualified stock options granted (in shares)	87,900
Per share weighted average exercise price (in dollars per share)	$ 59.72
Per share weighted average grant date fair value (in dollars per share)	$ 16.47
Performance units
Additional disclosures
Granted (in shares)	45,100
Percentage of target to be awarded, low end of range	40.00%
Percentage of target to be awarded, high end of range	200.00%
Common stock earned as a percentage of the performance unit target	90.00%
Market price at grant date of performance units	$ 59.72
Nonqualified stock options and SARs
Stock options and SARs vested
Vested (in shares)	89,600
Aggregate grant date fair value	0.9
Omnibus Plan
Stock Compensation Plans
Additional common stock reserved for issuance subject to shareholders approval (in shares)	1,577,000
Par value of shares of common stock (in dollars per share)				$ 0.01
Shares of common stock reserved for future issuance	1,320,000			3,500,000
LTIP | Stock options | Participants
Additional disclosures
Shares outstanding that vested and would have been exercisable had the participants reached retirement age	50,000
Aggregate grant date fair value of options subject to accelerated vesting	$ 0.5