Share-Based Compensation - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Repurchase of common stock for employee tax withholding obligations amount			$ 2,994,000	$ 1,024,000
2017 Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Useful Life of the plan			10 years
Common stock shares issuable	1,750,000		1,750,000
Shares available for grant	1,581,743		1,581,743
2007 Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award vesting period			3 years
2007 Plan | Performance Unit Incentive Plan (“PUP”)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Awards with grant date fair value during the period			$ 4,300,000
Stock value payable			1,700,000
Liability awards recorded	$ 4,200,000		4,200,000		$ 7,000,000.0
Payments to employees			$ 5,600,000		5,900,000
Repurchase of common stock for employee tax withholding obligations amount, shares			25,771
Repurchase of common stock for employee tax withholding obligations amount			$ 1,500,000
Paid to employees as shares			$ 3,400,000
2007 Plan | Restricted Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Repurchase of common stock for employee tax withholding obligations amount, shares			24,217	19,237
Repurchase of common stock for employee tax withholding obligations amount			$ 1,400,000	$ 1,000,000.0
Unamortized cost	4,100,000		$ 4,100,000
Recognition period of unrecognized cost			1 year 6 months
2007 Plan | Restricted Stock Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Payments to employees			$ 300,000	200,000
Liabilities related to restricted stock	300,000		300,000		$ 400,000
Payments to employees in shares			200,000
Restructuring Charges
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation before income tax benefit	$ 0	$ 0	$ 0	$ 0