Derivative Instruments and Hedging Activities (Components of Gain (Loss) on Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Unrealized gain due to change in fair market value	$ (26,478)	$ (22,010)	$ 822	$ (8,052)
Realized gain (loss) on settlement	(3,534)	(98)	(7,855)	(3,813)
Total gain (loss) on derivative instruments	(30,012)	(22,108)	(7,033)	(11,865)
Parent Company [Member]
Total gain (loss) on derivative instruments	$ (30,012)	$ (22,108)	$ (7,033)	$ (11,865)