Summary of Significant Accounting Policies - Basic and diluted loss per share (Details 1) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income (loss) per consolidated statements of income (loss)	$ 2,296	$ 311	$ 268	$ 591	$ (4,745)	$ (905)	$ 582	$ 1,420	$ 3,466	$ (3,648)
Less: Allocation of income (loss) to participating securities									(32)
Net income (loss) allocated to common stock									3,434	(3,648)
Basic income (loss) per share computation:
Net income (loss) allocated to common stock									$ 3,434	$ (3,648)
Weighted average common shares outstanding, including shares considered participating securities									7,774	7,861
Less: Weighted average participating securities outstanding									(72)
Weighted average shares of common stock									7,702	7,861
Basic income (loss) per share	$ 0.31	$ 0.04	$ 0.03	$ 0.07	$ (0.60)	$ (0.12)	$ 0.07	$ 0.18	$ 0.45	$ (0.46)
Diluted income (loss) per share computation:
Income (loss) allocated to common stock									$ 3,434	$ (3,648)
Undistributed earnings re-allocated to participating securities									32
Numerator for diluted income (loss) per share									$ 3,466	$ (3,648)
Weighted average common shares outstanding for basic income (loss) per share									7,702	7,861
Incremental shares from stock options									1
Weighted average shares and dilutive potential common shares									7,703	7,861
Diluted income (loss) per share	$ 0.31	$ 0.04	$ 0.03	$ 0.07	$ (0.60)	$ (0.12)	$ 0.07	$ 0.18	$ 0.45	$ (0.46)