Condensed Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 10,799	$ 13,927	$ 50,287	$ (488,585)
Derivative financial instruments:
Reclassification adjustment for gain included in net income (loss)	(1)		(4)	(3)
Investments in marketable securities:
Unrealized holding loss		(1)		(6,559)
Reclassification adjustment for loss included in net income (loss)				11,600
Total other comprehensive (loss) gain	(1)	(1)	(4)	5,038
Comprehensive income (loss)	$ 10,798	$ 13,926	$ 50,283	$ (483,547)