Business Combinations - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 17, 2019	Mar. 31, 2019	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Proceeds from lines of credit			$ 0	$ 36,500	$ 0	$ 80,500	$ 8,500	$ 80,500	$ 35,700	$ 80,500	$ 0
Goodwill	$ 25,188		$ 7,587	$ 7,941	$ 7,624	$ 7,658	25,188	$ 7,374	27,816	7,576
First Source Electronics, LLC
Business Acquisition [Line Items]
Payments to acquire businesses, gross		$ 34,000
Business combination, contingent consideration arrangements	5,600	10,800					5,600
Business combination, contingent consideration, liability	4,700						$ 4,700
Escrow deposit		3,000
Business combination, pro forma information, Revenue of Acquiree since acquisition date, actual									12,800
Business combination, net income									18,324	$ 44,139
Business combination, acquisition related costs									900
Goodwill		20,365
Increase in goodwill valuation	$ 2,700
Third ARLS Agreement | Revolving Credit Facility | Line of Credit | First Source Electronics, LLC
Business Acquisition [Line Items]
Proceeds from lines of credit		$ 2,000
Minimum | First Source Electronics, LLC
Business Acquisition [Line Items]
Payments for milestones depreciation and amortization percent		90.00%
Maximum | First Source Electronics, LLC
Business Acquisition [Line Items]
Payments for milestones depreciation and amortization percent		100.00%
Electrical Systems | First Source Electronics, LLC
Business Acquisition [Line Items]
Business combination, net income									$ 200