Significant Accounting Policies, Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance				$ 99,565
Net current period other comprehensive income (loss)		$ 88	$ (10,738)	(14)	$ (13,288)
Ending balance		215,571		215,571
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(30,460)	(16,115)	(30,358)	(13,565)
Ending balance		(30,372)	(26,853)	(30,372)	(26,853)
Unrealized Losses on Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications, net of tax	[1]	130	(10,738)	396	(13,288)
Amounts reclassified from accumulated other comprehensive income (loss)		0	0	(374)	0
Other comprehensive income (loss), tax		0	0	0	0
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss) before reclassifications, net of tax		$ (42)	$ 0	$ (36)	$ 0

[1] There was no tax expense or benefit related to elements of other comprehensive income (loss) for the three and six months ended June 30, 2017 and 2016.