Warrants, Recurring Level 3 Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) [Abstract]
Warranty liability	$ 0	$ 615	$ 263	$ 24	$ 67	$ 255	$ 676	$ 1,333	$ 662
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) [Abstract]
Warranty liability	0				0
Significant other Observable Inputs (Level 2) [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) [Abstract]
Warranty liability	0				0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) [Abstract]
Warranty liability	$ 0				$ 67