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Segment Information - Geographic Information on Sales to External Customers (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Segment Reporting, Revenue Reconciling Item [Line Items]                      
Sales to external customers $ 346,140 $ 296,129 $ 288,775 $ 265,765 $ 296,031 $ 278,233 $ 295,998 $ 279,268 $ 1,196,809 $ 1,149,530 $ 1,130,783
United States                      
Segment Reporting, Revenue Reconciling Item [Line Items]                      
Sales to external customers                 622,276 580,724 593,539
Other                      
Segment Reporting, Revenue Reconciling Item [Line Items]                      
Sales to external customers                 $ 574,533 $ 568,806 $ 537,244