Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Feb. 28, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net unrealized holding gains (losses) on investments arising during the period, tax provision (benefit)	$ 107	$ (370)
Less: reclassification adjustment for net (gains) losses included in net income (loss), tax provision (benefit)	(377)	(5)
Net change in unrealized holding gains (losses) on investments, tax provision (benefit)	484	(365)
Net unrealized foreign exchange gains (losses) arising during the period, tax provision (benefit)	7,722	1,926
Less: reclassification adjustment for foreign exchange (gains) losses included in net income (loss), tax provision (benefit)	0	0
Net change in unrealized foreign exchange gains (losses), tax provision (benefit)	7,722	1,926
Net unrealized gains (losses) on instrument specific credit risk arising during the period, tax provision (benefit)	5,949	(4,634)
Less: reclassification adjustment for instrument specific credit risk (gains) losses included in net income (loss), tax provision (benefit)	(99)	0
Net change in unrealized instrument specific credit risk gains (losses), tax provision (benefit)	6,048	(4,634)
Net unrealized gains (losses) on cash flow hedges arising during the period, net of income tax provision (benefit) of $(86) and $1,234	(86)	1,234
Less: reclassification adjustment for cash flow hedges (gains) losses included in net income (loss), tax provision (benefit)	0	0
Net change in unrealized cash flow hedges gains (losses), tax provision (benefit)	(86)	1,234
Net pension gains (losses) arising during the period, tax provision (benefit)	0	0
Less: reclassification adjustment for pension (gains) losses included in net income (loss), tax provision (benefit)	(119)	(151)
Net change in pension liability, tax provision (benefit)	$ 119	$ 151