Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Revenues by destination (Details 2)

v3.8.0.1
Summary of Significant Accounting Policies - Revenues by destination (Details 2) - 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
Schedule Of Significant Accounting Policies [Line Items]                      
Revenues $ 1,249,553 $ 1,651,738 $ 1,344,103 $ 1,150,781 $ 1,125,137 $ 1,484,736 $ 1,186,835 $ 1,077,632 $ 5,396,175 $ 4,874,340 $ 4,345,048
North America                      
Schedule Of Significant Accounting Policies [Line Items]                      
Revenues                 3,285,903 3,132,208 2,743,007
Europe                      
Schedule Of Significant Accounting Policies [Line Items]                      
Revenues                 1,347,381 1,148,403 1,120,705
Asia Pacific                      
Schedule Of Significant Accounting Policies [Line Items]                      
Revenues                 394,631 196,978 198,131
Other                      
Schedule Of Significant Accounting Policies [Line Items]                      
Revenues                 $ 368,260 $ 396,751 $ 283,205