Property, plant and equipment (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Property, Plant and Equipment [Line Items]      
Property, plant and equipment $ 321,611,000 $ 284,707,000  
Less: Accumulated depreciation and amortization (57,371,000) (42,943,000)  
Total Property, plant and equipment, net 264,240,000 241,764,000  
Impairment related to equipment 1,200,000    
Depreciation and amortization expense 18,958,000 11,197,000 9,355,000
Land and improvements [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 10,605,000 4,839,000  
Buildings, building improvements and leasehold improvements [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 83,823,000 66,953,000  
Furniture and equipment [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 107,006,000 91,772,000  
Software [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment 21,832,000 15,691,000  
Construction-in-progress [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment $ 98,345,000 $ 105,452,000