Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies (Narrative) (Details)

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Commitments and Contingencies (Narrative) (Details)
12 Months Ended
Dec. 31, 2017
USD ($)
yr
Inventories [Member]  
Loss Contingencies [Line Items]  
Outstanding inventory purchase obligations | $ $ 266,507,000
Minimum [Member]  
Loss Contingencies [Line Items]  
Operating leases, base lease term 5
Maximum [Member]  
Loss Contingencies [Line Items]  
Operating leases, base lease term 10