Stock-Based Compensation - Performance-based Awards (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 31, 2019	Jun. 30, 2017
Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved							425,000
Performance-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved	600,000
Stock-based compensation expense	$ 0.0
Performance-based awards | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved						200,000	200,000
Stock-based compensation expense		$ 0.2	$ 0.1	$ 0.2	$ 0.3
Restricted stock units | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved						100,000
Stock-based compensation expense		0.2		0.2
Restricted stock units | Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved						100,000
Restricted stock units | Chief Operating Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved						100,000
Restricted stock units | Chief Financial Officer and Chief Operating Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 0.4		$ 0.4