Income taxes - Schedule of Provision for Income Taxes (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Current tax provision (benefit):      
U.S. federal $ (131) $ 383 $ 6,105
State (792) 1,201 2,136
Foreign 54,076 63,692 56,029
Total current 53,153 65,276 64,270
Deferred tax provision (benefit):      
U.S. federal 62,672 (29,962) 12,434
State 2,306 (484) (753)
Foreign 6,629 4,716 3,091
Total deferred 71,607 (25,730) 14,772
Provision for income taxes $ 124,760 $ 39,546 $ 79,042