Derivative Instruments and Hedging Activities (Components of Gain (Loss) on Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Change in fair market value	$ (20,884)	$ (9,491)	$ 11,475
Loss on settlement	(11,477)	(3,814)	(17,345)
Total loss on derivative instruments	(32,361)	(13,305)	(5,870)
Parent Company [Member]
Total loss on derivative instruments	$ (32,361)	$ (13,305)	$ (5,870)