Detail of Certain Balance Sheet Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Activity in allowance for doubtful accounts
Balance at beginning of year	$ 3,400	$ 4,288	$ 5,158
Bad debt expense (benefit)	3,562	182	(27)
Deductions for uncollectible receivables written off, net of recoveries	(1,304)	(1,829)	(876)
Allowance for doubtful accounts of acquired companies at date of acquisition	240	759	33
Balance at end of year	5,898	3,400	$ 4,288
Other current liabilities
Accrued warranty costs	6,453	6,149
Accrued job losses	1,495	598
Accrued sales and use tax	2,685	2,308
Deferred revenue	5,233	3,895
Liabilities due to former owners	2,045	2,981
Other current liabilities	14,941	17,723
Total other current liabilities	$ 32,852	$ 33,654