Stock-Based Compensation - Fair Value Assumptions (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares
Fair value assumptions:
Expected term			5 years 3 months 18 days
Additional information
Stock-based compensation expense | $	$ 6.9	$ 5.9	$ 7.2
Stock Options
Stock-Based Compensation
Weighted-average fair value per share of options granted (in dollars per share)			$ 13.06
Fair value assumptions:
Expected dividend yield (as a percent)			0.79%
Expected stock price volatility (as a percent)			31.70%
Risk-free interest rate (as a percent)			2.66%
Other information
Compensation expense yet to be recognized | $	$ 0.1
Weighted-average period over which compensation cost will be recognized	3 months 18 days
Total fair value of options vested | $	$ 0.7
Nonvested Options, Shares
Nonvested at beginning of year (in shares) | shares	81
Vested (in shares) | shares	(54)
Nonvested at end of year (in shares) | shares	27	81
Nonvested Options, Weighted-Average Grant Date Fair Value
Nonvested at beginning of year (in dollars per share)	$ 12.53
Granted (in dollars per share)			$ 13.06
Vested (in dollars per share)	12.26
Nonvested at end of year (in dollars per share)	$ 13.06	$ 12.53
Additional information
Vesting period	3 years
Restricted Stock and Restricted Stock Units
Other information
Compensation expense yet to be recognized | $	$ 1.1
Weighted-average period over which compensation cost will be recognized	1 year 9 months 18 days
Shares
Unvested at beginning of year (in shares) | shares	91
Granted (in shares) | shares	118
Vested (in shares) | shares	(85)
Forfeited (in shares) | shares	(4)
Unvested at end of year (in shares) | shares	120	91
Weighted Average Grant Date Fair Value
Unvested at beginning of year (in dollars per share)	$ 47.58
Granted (in dollars per share)	39.03	$ 51.02	44.02
Vested (in dollars per share)	39.13
Forfeited (in dollars per share)	45.21
Unvested at end of year (in dollars per share)	$ 45.21	47.58
Additional information
Fair value of shares vested | $	$ 3.3
Weighted-average fair value (in dollars per share)	$ 39.03	$ 51.02	$ 44.02
Aggregate intrinsic value of restricted stock vested | $	$ 2.9	$ 3.5	$ 3.3
Performance Stock Units
Other information
Compensation expense yet to be recognized | $	$ 0.7
Weighted-average period over which compensation cost will be recognized	1 year 4 months 24 days
Additional information
Vesting period	3 years
Types of performance units | item	2
Percentage of units measured on stock price relative to peer group	50.00%
Percentage of units measured on stock price based on pre determined EPS	50.00%
Period for which shareholder return is compared with peer group for units determined by EPS performance	3 years
Calculated fair market value | $	$ 6.2
Value of PSUs granted | $	2.2
Stock-based compensation expense | $	$ 2.7	$ 1.9	$ 2.9
Performance Stock Units | Minimum
Additional information
Performance measures for dollar denominated award granted	0
Performance Stock Units | Maximum
Additional information
Performance measures for dollar denominated award granted	2.0