Variable interest entities (Details) (USD $)	9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Carrying amounts of consolidated assets and liabilities of variable interest entities
Current assets	$ 338,188,000	$ 398,731,000
Property, plant and equipment	1,205,343,000	1,268,837,000
Goodwill	176,308,000	177,498,000
Other assets	19,953,000	23,711,000
Total assets	2,005,658,000	2,137,714,000
Current liabilities	(227,344,000)	(256,511,000)
Third-party debt, current portion	1,766,000	1,775,000
Deferred income taxes	(61,835,000)	(61,835,000)
Total liabilities	(1,016,047,000)	(1,070,819,000)
Charleston Center LLC
Variable interest entities
Ownership percentage	19.90%
Carrying amounts of consolidated assets and liabilities of variable interest entities
Current assets	9,380,000	5,897,000
Property, plant and equipment	186,969,000	188,502,000
Goodwill	40,395,000	40,395,000
Other assets	2,456,000	2,823,000
Total assets	239,200,000	237,617,000
Current liabilities	(21,612,000)	(17,827,000)
Third-party debt, including $1,766 and $1,775 current portion	(90,974,000)	(92,304,000)
Third-party debt, current portion	1,766,000	1,775,000
Deferred income taxes	(61,835,000)	(61,835,000)
Total liabilities	(174,421,000)	(171,966,000)
Net assets (before amounts payable to OEH of $93,196 and $94,141)	64,779,000	65,651,000
Amounts payable to OEH	$ 93,196,000	$ 94,141,000