Divestiture and Discontinued Operations - Summary of financial information of discontinued operations (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Summarized financial results
Provision for income taxes	$ 0	$ (100)
PAR Springer Miller Systems Inc
Summarized financial results
Income from discontinued operations before income taxes	0	284
Provision for income taxes	0	(60)
Income from discontinued operations, net of taxes	$ 0	$ 224

Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

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