Property, plan and equipment - Textuals (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Depreciation	$ 43,444	$ 43,335	$ 42,029
Impairment of real estate assets, other intangible assets and property, plant and equipment	3,837	8,153	7,456
Property, plant and equipment	1,171,603	1,107,595
Interest costs capitalized	4,193	863	2,201
Charleston Center LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	183,793	185,788
Casa de Sierra Nevada San Miguel de Allende
Property, Plant and Equipment [Line Items]
Non-cash property, plant and equipment impairment charge		$ 8,153