Immaterial Restatement (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Depreciation and amortization	$ 127,339	$ 125,837	$ 128,856
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(1,154,456)	(1,063,188)
Assets	2,027,622	2,055,958
Deferred Tax Liability	156,740	133,767
Limited Partners' Capital Account	182,469	165,518
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	132,581	81,963	(30,382)
Income Tax Expense (Benefit)	31,365	11,217	2,670
Net income (loss)	101,216	70,746	(33,052)
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic	1.82	1.28	(0.6)
Net income (loss) per limited partner unit	1.81	1.27	(0.6)
Restatement Adjustment [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Depreciation and amortization		2,032	2,060
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		(18,599)
Assets		(18,599)
Deferred Tax Liability		(1,679)
Limited Partners' Capital Account		(16,920)
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest		(2,032)	(2,060)
Income Tax Expense (Benefit)		(620)	(575)
Net income (loss)		(1,412)	(1,485)
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic		(0.02)	(0.03)
Net income (loss) per limited partner unit		(0.02)	(0.03)
Scenario, Previously Reported [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Depreciation and amortization		123,805	126,796
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		(1,044,589)
Assets		2,074,557
Deferred Tax Liability		135,446
Limited Partners' Capital Account		182,438
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest		83,995	(28,322)
Income Tax Expense (Benefit)		11,837	3,245
Net income (loss)		$ 72,158	$ (31,567)
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic		1.3	(0.57)
Net income (loss) per limited partner unit		1.29	(0.57)