Stock Compensation Plan (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Options
Stock options awarded
Options granted (in shares)	143,726
Per share weighted average exercise price (in dollars per share)	$ 82.11
Per share weighted average grant date fair value (in dollars per share)	$ 13.54
Fair value assumptions
Expected term in years	5 years 8 months 12 days
Risk free interest rate (as a percent)	2.10%
Volatility (as a percent)	22.90%
Dividend yield (as a percent)	3.00%
Stock options and Stock Appreciation Rights vested
Options vested (in shares)	92,107
Aggregate grant date fair value of Options vested	$ 1.4
Outstanding Stock Options and Stock Appreciation Rights
Options outstanding (in shares)	534,885	530,462
Aggregate intrinsic value (in dollars)	$ 12.4	$ 25.0
Per share weighted average exercise price (in dollars per share)	$ 53.51	$ 38.35
Exercisable Options (in shares)	289,140	336,336
Aggregate intrinsic value (in dollars)	$ 10.7	$ 19.3
Unvested Options (in shares)	245,745	194,126
Per share weighted average grant date fair value (in dollars per share)	$ 14.31	$ 15.15
Performance Share Units ("PSUs")
Additional disclosures
Granted (in shares)	41,748
Percentage of target to be awarded, low end of range (not less than)	40.00%
Percentage of target to be awarded, high end of range (not more than)	200.00%
Market price at grant date of performance units (in dollars per share)	$ 82.15