Supplemental Consolidated Balance Sheet and Statement of Operations Information - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Accrued Liabilities and Other Liabilities [Abstract]
Accrued vacation	$ 8,353		$ 6,906
Accrued commissions	5,561		7,265
Accrued bonuses	7,121		5,643
Estimated health insurance claims	1,040		1,100
ESPP employee contributions	3,734		2,156
Customer deposits	12,151		7,395
Operating lease liabilities	3,064
Accrued other liabilities	8,906		5,888
Accrued expenses and other current liabilities	$ 49,930	$ 38,672	$ 36,353