Discontinued Operations and Assets Held for Sale (Table Illustration of Discontinued Operations in Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Discontinued Operations
Revenues	$ 8,284	$ 194,166	$ 248,024
Operating expenses	(3,286)	(89,123)	(107,412)
Depreciation and Amortization, Discontinued Operations	(3,454)	(59,453)	(84,139)
Operating income	1,544	45,590	56,473
Interest expense	(3,093)	(47,356)	(63,556)
Loss before gain on sales	(1,549)	(1,766)	(7,083)
Gain on sale of depreciable properties	13,467	100,882	33,054
Income (loss) from discontinued operations	$ 11,918	$ 99,116	$ 25,971