Stock Incentive Plans (Details 2) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options Granted
Share-based Payment Arrangement, Exercise of Option, Tax Benefit	$ 1.9	$ 2.2	$ 7.4
Options, additional information
Total unrecognized stock-based compensation expense	$ 2.0
Weighted-average period over which this expense will be recognized	9 months 18 days
Employee nonstatutory stock options
Stock Incentive Plans
Number Outstanding (in shares)	1,565,609
Number Exercisable (in shares)	1,059,016
Weighted-average remaining contractual term of exercisable options (in years)	2 years 5 months 23 days
Options Granted
Options granted (in shares)	189,787	428,190	316,830
Stock or Unit Option Plan Expense	$ 3.1	$ 5.8	$ 4.3
Assumptions used for estimating the fair value of stock options
Weighted average expected volatility (as a percent)	23.00%	23.70%	24.80%
Risk-free rate	2.58%	2.55%	1.66%
Dividend yield	1.40%	1.40%	1.20%
Volatility rate, minimum	22.70%	22.90%	23.80%
Volatility rate, maximum	23.10%	24.40%	25.10%
Employee nonstatutory stock options | Minimum
Assumptions used for estimating the fair value of stock options
Expected term	5 years 6 months	3 years	3 years
Employee nonstatutory stock options | Maximum
Assumptions used for estimating the fair value of stock options
Expected term	6 years 6 months	6 years 6 months	4 years
Employee nonstatutory stock options | Exercise Price Range One [Member]
Stock Incentive Plans
Exercise price, low	$ 0
Exercise price, high	10
Employee nonstatutory stock options | Exercise Price Range Two [Member]
Stock Incentive Plans
Exercise price, low	10
Exercise price, high	20
Employee nonstatutory stock options | Exercise Price Range Three [Member]
Stock Incentive Plans
Exercise price, low	20
Exercise price, high	30
Employee nonstatutory stock options | Exercise Price Range Four [Member]
Stock Incentive Plans
Exercise price, low	30
Exercise price, high	40
Employee nonstatutory stock options | Exercise Price Range Five [Member]
Stock Incentive Plans
Exercise price, low	40
Exercise price, high	50
Employee nonstatutory stock options | Exercise Price Range Six [Member]
Stock Incentive Plans
Exercise price, low	50
Exercise price, high	60
Employee nonstatutory stock options | Exercise Price Range Seven [Member]
Stock Incentive Plans
Exercise price, low	60
Exercise price, high	$ 70
Number Outstanding (in shares)	668,479
Number Exercisable (in shares)	428,259
Outstanding Weighted- Average Remaining Contractual Life (Years)	2 years 2 months 23 days
Weighted-Average Exercise Price (in dollars per share)	$ 67.98
Employee nonstatutory stock options | Exercise Price Range Eight [Member]
Stock Incentive Plans
Exercise price, low	70
Exercise price, high	$ 80
Number Outstanding (in shares)	897,130
Number Exercisable (in shares)	630,757
Outstanding Weighted- Average Remaining Contractual Life (Years)	2 years 7 months 28 days
Weighted-Average Exercise Price (in dollars per share)	$ 75.59
Employee nonstatutory stock options | Exercise Price Range Nine [Member]
Stock Incentive Plans
Exercise price, low	80
Exercise price, high	90
Employee nonstatutory stock options | Exercise Price Range Ten [Member]
Stock Incentive Plans
Exercise price, low	90
Exercise price, high	100
Employee nonstatutory stock options | Exercise Price Range Eleven [Member]
Stock Incentive Plans
Exercise price, low	100
Exercise price, high	$ 110
Restricted Stock Units (RSUs) and Performance Stock Units (PSUs) [Member]
Stock Incentive Plans
Share-based Payment Arrangement, Expense	$ 9.2	$ 13.2	$ 10.3