Equity Compensation Plans - Narrative (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Apr. 27, 2012	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense		$ 1.4	$ 1.1	$ 2.6	$ 2.3
Stock options granted (shares)		0	0	11,180	0
Stock options exercised (shares)			16,300	27,041	28,464
Cash received from exercise of stock option			$ 0.2	$ 0.7	$ 0.3
Intrinsic value of options exercised			0.7	0.7	1.2
Intrinsic value of stock options exercised, tax benefit			$ 0.1	$ 0.1	$ 0.3
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award, term				10 years
Total unrecognized compensation cost		$ 2.9		$ 2.9
Weighted average expected amortization period				2 years 9 months
Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award, vesting period				3 years
Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award, vesting period				4 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost		$ 4.8		$ 4.8
Weighted average expected amortization period				2 years
Unvested restricted stock awards (shares)		187,902		187,902
Time Based Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted (shares)			0	8,106	0
Restricted shares vested (shares)			0	5,164	9,288
Time Based Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award, vesting period				2 years
Time Based Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award, vesting period				4 years
Performance Based Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted (shares)			0	15,190	18,100
Restricted shares vested (shares)			0	48,035	108,600
Stock Option Plan 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share options and restricted shares authorized (shares)	1,750,000
Additional shares authorized under the plan (shares)	1,200,000