Stock Compensation Plans - Omnibus Plan (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2004
Stock Compensation Plans
Par value of shares of common stock (in dollars per share)	$ 0.01	$ 0.01
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 5.6	$ 4.0	$ 6.4
Income tax benefit	(1.4)	(1.0)	(2.5)
Stock-based compensation, net of income tax benefit	4.2	3.0	3.9
Compensation costs related to equity awards and amounts recognized
Compensation expense recognized	$ (5.6)	(4.0)	$ (6.4)
Stock options awarded
Nonqualified stock options granted (in shares)	1,272
Per share weighted-average grant date fair value (in dollars per share)	$ 10.32
Number of Stock Options
Add: Options granted (in shares)	1,272
Stock Options
Stock Compensation Plans
Expiration period				10 years
Vesting period				3 years
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 0.4
Compensation costs related to equity awards and amounts recognized
Unrecognized compensation cost at the beginning of the period	0.6
Grant date fair value current year grants	0.0
Compensation expense recognized	(0.4)
Unrecognized compensation cost at the end of the period	$ 0.2	0.6
Expected amortization period	1 year 1 month 6 days
Performance Shares and RSUs
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 5.2
Compensation costs related to equity awards and amounts recognized
Unrecognized compensation cost at the beginning of the period	2.1
Grant date fair value current year grants	5.5
Compensation expense recognized	(5.2)
Unrecognized compensation cost at the end of the period	$ 2.4	$ 2.1
Expected amortization period	1 year 7 months 6 days
Options
Fair value assumptions
Expected term in years	5 years	5 years 8 months 12 days	5 years 9 months 18 days
Risk free interest rate (as a percent)	1.80%	2.50%	2.10%
Volatility (as a percent)	23.10%	21.50%	22.90%
Dividend yield (as a percent)	3.00%	3.00%	3.00%
Nonqualified stock options
Stock options awarded
Nonqualified stock options granted (in shares)	1,272	108,420	144,089
Per share weighted-average exercise price (in dollars per share)	$ 66.59	$ 93.22	$ 82.11
Per share weighted-average grant date fair value (in dollars per share)	$ 10.32	$ 15.00	$ 13.54
Number of Stock Options
Add: Options granted (in shares)	1,272	108,420	144,089
Weighted-Average Exercise Price
Add: Options granted (in dollars per share)	$ 66.59	$ 93.22	$ 82.11
RSUs | Non-employee members of the board of directors
Stock Compensation Plans
Vesting period	1 year
Omnibus Plan
Stock Compensation Plans
Shares of common stock reserved for future issuance				3,500,000
Par value of shares of common stock (in dollars per share)				$ 0.01
Stock options awarded
Nonqualified stock options granted (in shares)	1,272
Per share weighted-average exercise price (in dollars per share)	$ 66.59
Number of Stock Options
Options outstanding at the beginning of the period (in shares)	451,081
Add: Options granted (in shares)	1,272
Less: Options exercised (in shares)	34,073
Less: Options forfeited/cancelled (in shares)	1,732
Options outstanding at the end of the period (in shares)	416,548	451,081
Weighted-Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 67.46
Add: Options granted (in dollars per share)	66.59
Less: Options exercised (in dollars per share)	35.26
Less: Options forfeited/cancelled (in dollars per share)	71.89
Options outstanding at the end of the period (in dollars per share)	$ 70.08	$ 67.46
Omnibus Plan 2018
Stock Compensation Plans
Shares of common stock reserved for future issuance	1,091,000
Additional common stock reserved for issuance subject to shareholders approval (in shares)		800,000
Reduction in number of shares available for future issuance (in shares)	177,000