XML 69 R58.htm IDEA: XBRL DOCUMENT v3.8.0.1
Commitments and Contingencies - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Long Term Purchase Commitment [Line Items]    
Unconditional purchase obligations, term 4 years  
Unconditional purchase obligations $ 81,109  
Bank of America, N.A.    
Long Term Purchase Commitment [Line Items]    
Amount outstanding under letters of credit $ 1,271 $ 834
Minimum    
Long Term Purchase Commitment [Line Items]    
Unconditional purchase obligations, term 1 year  
Maximum    
Long Term Purchase Commitment [Line Items]    
Unconditional purchase obligations, term 4 years