Stock-Based Compensation - Performance-based Awards (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Jan. 31, 2019	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 4,051,000	$ 3,154,000
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		$ 200,000	$ 200,000
Restricted stock units | Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option shares approved				100,000
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