Disposed and Discontinued Operations - Assets and Liabilities of Discontinued Operations (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disposed and Discontinued Operations
Cash and cash equivalents		$ 5,251	$ 7,754
Other current assets		406
Inventories	$ 30	198
Current assets of discontinued operations	30	5,855
Other assets		67
Deferred income tax assets	269	5,917
Non-current assets of discontinued operations	269	5,984
Accounts payable and other accrued expenses		350
Accrued warranty	914	4,936
Current liabilities of discontinued operations	914	5,286
Accrued warranty	698	10,429
Other liabilities	189	286
Non-current liabilities of discontinued operations	$ 887	$ 10,715