Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2019	Jun. 30, 2018	May 31, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net unrealized holding gains (losses) on investments arising during the period, tax provision (benefit)	$ 31	$ 227	$ 138	$ (143)
Less: reclassification adjustment for net (gains) losses included in net income (loss), tax provision (benefit)	(544,677)	42	(545,054)	37
Net change in unrealized holding gains (losses) on investments, tax provision (benefit)	544,708	185	545,192	(180)
Net unrealized foreign exchange gains (losses) arising during the period, tax provision (benefit)	(10,439)	(2,719)	(2,717)	(793)
Less: reclassification adjustment for foreign exchange (gains) losses included in net income (loss), tax provision (benefit)	0	(16)	0	(16)
Net change in unrealized foreign exchange gains (losses), tax provision (benefit)	(10,439)	(2,703)	(2,717)	(777)
Net unrealized gains (losses) on instrument specific credit risk arising during the period, tax provision (benefit)	858	8,875	6,807	4,241
Less: reclassification adjustment for instrument specific credit risk (gains) losses included in net income (loss), tax provision (benefit)	(67)	78	(166)	78
Net change in unrealized instrument specific credit risk gains (losses), tax provision (benefit)	925	8,797	6,973	4,163
Net unrealized gains (losses) on cash flow hedges arising during the period, net of income tax provision (benefit) of $(86) and $1,234	86	(721)	0	513
Less: reclassification adjustment for cash flow hedges (gains) losses included in net income (loss), tax provision (benefit)	161	0	161	0
Net change in unrealized cash flow hedges gains (losses), tax provision (benefit)	(75)	(721)	(161)	513
Net pension gains (losses) arising during the period, tax provision (benefit)	0	0	0	0
Less: reclassification adjustment for pension (gains) losses included in net income (loss), tax provision (benefit)	(122)	(188)	(241)	(339)
Net change in pension liability, tax provision (benefit)	$ 122	$ 188	$ 241	$ 339