Significant Accounting Policies, Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ 365,280
Net current period other comprehensive loss		(1,475)	$ (102)
Ending balance		387,101
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(31,759)	(30,358)
Ending balance		(33,234)	(30,460)
Unrealized Gains (Losses) on Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications, net of tax	[1]	(1,530)	266
Amounts reclassified from accumulated other comprehensive income (loss)	[2]	0	(374)
Other comprehensive income (loss), tax		0	0
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications, net of tax		$ 55	$ 6

[1] There was no tax benefit for other comprehensive loss for the three months ended March 31, 2018 and 2017.

[2] Amounts are included in investment income on our condensed consolidated statement of operations.