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Commitments and Contingencies - Capital Commitments and Purchase Obligations (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Capital Expenditure Commitments      
Capital expenditures under current construction program for 2017 $ 36,700    
Contractual commitment to spend on capital expenditures 11,000    
Purchase obligations      
Obligations to purchase various goods and services 57,300    
Obligations to be incurred in 2017 33,500    
Other Lease Agreements      
Operating Lease Commitments      
Total rental expense 40,300 $ 37,900 $ 33,300
Future minimum lease commitments relating to the base lease rent portion of noncancelable operating leases      
2017 5,366    
2018 4,379    
2019 2,393    
2020 1,184    
2021 999    
Thereafter 13,959    
Total $ 28,280