Unaudited Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Unaudited Consolidated Statements of Comprehensive Income (Loss) [Abstract]
Net income (loss)	$ (12,343)	$ 5,969	$ (5,588)	$ 20,081
Unrealized net gains on securities:
Unrealized net gains arising during the period	5,147	3,348	11,137	2,572
Less: reclassification adjustment for net gains (losses) included in net income (loss)	1,667	(452)	2,322	6,822
Change in unrealized gains (losses) on investments	3,480	3,800	8,815	(4,250)
Foreign currency translation adjustments	388	124	453	543
Other comprehensive income (loss)	3,868	3,924	9,268	(3,707)
Comprehensive income (loss)	$ (8,475)	$ 9,893	$ 3,680	$ 16,374