Accumulated Other Comprehensive Income/(Loss) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Accumulated other comprehensive income/(loss)
Balances, beginning of period	$ 40,525
Balances, end of period	29,083
Accumulated other comprehensive income/(loss) net of tax
Balances, beginning of period	40,525
Balances, end of period	29,083
Accumulated Other Comprehensive Income/(Loss)
Accumulated other comprehensive income/(loss)
Balances, beginning of period	15
Balances, end of period	(2)
Accumulated other comprehensive income/(loss) net of tax
Balances, beginning of period	15
Balances, end of period	(2)
Accumulated Other Comprehensive Income/(Loss) \| Accounting Standards Update 2016-01
Accumulated other comprehensive income/(loss)
Cumulative adjustment related to Accounting Standard Update 2016-01	2
Accumulated due to realization of gain on marketable securities
Accumulated other comprehensive income/(loss)
Other comprehensive gain due to change in fair market value of marketable securities during period before reclassifications, before tax	(17)
Accumulated other comprehensive income/(loss) net of tax
Other comprehensive gain due to change in fair market value of marketable securities during period before reclassifications, net of tax	(14)
Accumulated other comprehensive income after tax
Accumulated other comprehensive income/(loss)
Balances, beginning of period	14
Accumulated other comprehensive income/(loss) net of tax
Balances, beginning of period	$ 14

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