Property, plant and equipment (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]
Property, plant and equipment	$ 284,707	$ 241,432
Less: Accumulated depreciation and amortization	(42,943)	(32,459)
Total Property, plant and equipment, net	241,764	208,973
Depreciation and amortization expense	11,197	9,355	5,990
Land and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	4,839	4,115
Buildings, building improvements and leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	66,953	26,122
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	91,772	42,135
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	15,691	11,854
Construction-in-progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 105,452	$ 157,206