Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (6,201)	$ (27,705)
Other comprehensive income (loss):
Unrealized gains (losses) from change in fair value based on instrument specific credit risk	580	1,266
Total other comprehensive income (loss)	580	1,266
Comprehensive income (loss)	$ (5,621)	$ (26,439)