401(K) Plan and Other Defined Contribution Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
The 401(K) Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, matching contribution, percent of employee's base salary	3.00%
Defined contribution plan, cost	$ 1,400	$ 1,200	$ 1,000
Defined contribution plan, employer discretionary contribution amount	1,500	489	126
EDCP
Defined Contribution Plan Disclosure [Line Items]
Compensation expense	$ 441	$ 238	$ 272