Disposed and Discontinued Operations - Assets and Liabilities of Discontinued Operations (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Disposed and Discontinued Operations
Cash and cash equivalents		$ 5,251	$ 7,444
Other current assets		406
Inventories	$ 84	198
Current assets of discontinued operations	84	5,855
Other assets		67
Deferred income tax assets	755	5,917
Non-current assets of discontinued operations	755	5,984
Accounts payable and other accrued expenses		350
Accrued warranty	910	4,936
Current liabilities of discontinued operations	910	5,286
Accrued warranty	903	10,429
Other liabilities	142	286
Non-current liabilities of discontinued operations	$ 1,045	$ 10,715