Stock-Based Compensation - Stock Award Information and Fair Value Assumptions (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Stock-based compensation
Compensation to be recognized over requisite service period			$ 23.9
Stock-based compensation expense
Total pre-tax stock-based compensation	$ 4.7	$ 3.9	$ 10.7	$ 8.6
Weighted-average assumptions used to estimate grant date fair value of stock options
Expected dividend yield (as a percent)			1.30%	1.40%
Expected life in years			5 years 6 months 29 days	5 years 7 months 9 days
Expected volatility (as a percent)			25.60%	27.50%
Risk-free interest rate (as a percent)			1.90%	1.40%
Weighted average fair value per share (in dollars per share)			$ 24.57	$ 19.30
Executive Incentive Program
Stock-based compensation
Shares available for grant under the plan (in shares)	3,446,306		3,446,306
Stock options
Stock-based compensation
Options granted (in shares)			364,675
Maximum term life			10 years
Stock-based compensation expense
Total pre-tax stock-based compensation	$ 1.9	$ 1.4	$ 3.8	$ 3.0
Stock options | Executive Incentive Program
Stock-based compensation
Shares available for grant under the plan (in shares)	1,295,490		1,295,490
Restricted stock
Stock-based compensation
Awards granted (in shares)			65,637
Performance shares
Stock-based compensation
Awards granted (in shares)			47,285
Restricted Stock Units
Stock-based compensation
Awards granted (in shares)			12,952
Portion of Stock Options Vesting on First Anniversary | Stock options
Stock-based compensation
Stock options vesting under graded vesting schedule (percent)			33.33%
Portion of Stock Options Vesting on Second Anniversary | Stock options
Stock-based compensation
Stock options vesting under graded vesting schedule (percent)			33.33%
Portion of stock Options Vesting on Third Anniversary | Stock options
Stock-based compensation
Stock options vesting under graded vesting schedule (percent)			33.33%