Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net unrealized holding gains (losses) on investments arising during the period, tax provision (benefit)	$ (424)	$ (598)	$ (567)	$ 5,106
Less: reclassification adjustment for net (gains) losses included in net income (loss), tax provision (benefit)	0	(257)	37	14
Net change in unrealized holding gains (losses) on investments, tax provision (benefit)	(424)	(341)	(604)	5,092
Net unrealized foreign exchange gains (losses) arising during the period, tax provision (benefit)	(3,367)	4,374	(4,160)	12,929
Less: reclassification adjustment for foreign exchange (gains) losses included in net income (loss), tax provision (benefit)	0	(11)	(16)	1,086
Net change in unrealized foreign exchange gains (losses), tax provision (benefit)	(3,367)	4,385	(4,144)	11,843
Net unrealized gains (losses) on instrument specific credit risk arising during the period, tax provision (benefit)	355	2,149	4,596	(5,270)
Less: reclassification adjustment for instrument specific credit risk (gains) losses included in net income (loss), tax provision (benefit)	48	0	126	0
Net change in unrealized instrument specific credit risk gains (losses), tax provision (benefit)	307	2,149	4,470	(5,270)
Net change in unrealized cash flow hedges gains (losses), tax provision (benefit)	0	0	513	0
Less: reclassification adjustment for pension (gains) losses included in net income (loss), tax provision (benefit)	$ (169)	$ (201)	$ (508)	$ (1,835)