Derivative Contracts - Derivative Gains (Losses) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	$ 5,482	$ 1,235	$ 9,519	$ (188)
Common Stock options/warrants
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	444	(3,730)	(512)	(4,716)
Notes
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	5,069	4,872	10,014	4,734
Forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gain (loss)	$ (31)	$ 93	$ 17	$ (206)