Equity Compensation Plans - Narrative (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Apr. 27, 2012	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense		$ 0.6	$ 1.0	$ 3.2	$ 3.2
Stock options granted (shares)		0	0	11,180	0
Stock options exercised (shares)		19,250	6,170	46,291	34,634
Cash received from exercise of stock option		$ 0.2	$ 0.1	$ 0.8	$ 0.4
Intrinsic value of options exercised		0.6	0.2	1.3	1.4
Intrinsic value of stock options exercised, tax benefit		0.1	$ 0.1	$ 0.3	$ 0.4
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award, term				10 years
Total unrecognized compensation cost		2.6		$ 2.6
Weighted average expected amortization period				2 years 7 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		$ 4.3		$ 4.3
Weighted average expected amortization period				1 year 11 months
Unvested restricted stock awards (shares)		179,772		179,772
Time Based Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted (shares)		10,790		18,896	0
Restricted shares vested (shares)		14,570	6,000	19,734	15,288
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	0	15,190	18,100
Restricted shares vested (shares)		0	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