Segment Information (Reconciliation of Segment Profit to Operating Income) (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
Segment Reporting [Abstract]
Segment profits	$ 60,882	$ 64,194	$ 186,996	$ 195,873
General and administrative	(16,364)	(17,349)	(53,930)	(46,729)
Gain (loss) on derivatives	(1,634)	(759)	(1,662)	1,977
Gain (loss) on sale of property	270	(109)	175	395
Depreciation, Amortization and Impairment, Total	(105,987)	(45,078)	(174,404)	(110,163)
Operating income (loss)	$ (62,833)	$ 899	$ (42,825)	$ 41,353