Accounting for the Impairment or Disposal of Long-Lived Assets - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 113,586,000	$ 137,476,000	$ 191,723,000
Operating expenses	41,875,000	48,956,000	73,462,000
Interest and other income	213,000	580,000	577,000
Interest expense	(15,903,000)	(19,783,000)	(29,058,000)
Depreciation and amortization	(29,566,000)	(30,739,000)	(44,297,000)
Income before property dispositions	26,455,000	38,578,000	45,483,000
Net gain on property dispositions included in discontinued operation	95,384,000	12,426,000	60,582,000
Net Income	121,839,000	51,004,000	106,065,000
Proceeds from Sale of Property, Plant, and Equipment	$ 491,800,000	$ 228,500,000	$ 365,200,000