Activity of Hedging Instruments in Accumulated OCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net unrealized loss on hedging instruments at January 1,			$ (196,305)
Unrealized gain (loss) on derivative instruments	$ 787	$ 2,895	998	$ 4,078
Realized losses reclassified into net income (loss)	(2,421)	(2,409)	(2,497)	(2,423)
Net unrealized loss on hedging instruments at June 30,	(194,349)		(194,349)
Accumulated Net Gain (Loss) from Derivative and Nonderivative Instruments Designated as Hedging Instruments [Member]
Net unrealized loss on hedging instruments at January 1,			(13,179)	(13,414)
Net unrealized loss on hedging instruments at June 30,	$ (14,678)	$ (11,759)	$ (14,678)	$ (11,759)