XML 54 R44.htm IDEA: XBRL DOCUMENT v3.7.0.1
Stock-based compensation - Summary of Restricted Stock Units (Detail) - Restricted Stock Units [Member]
shares in Thousands
6 Months Ended
Jun. 30, 2017
$ / shares
shares
Shares  
Unvested balance at beginning of period | shares 263
Granted | shares 266
Vested | shares (59)
Forfeited | shares (10)
Unvested balance at end of period | shares 460
Weighted-average grant date fair value  
Unvested balance at beginning of period | $ / shares $ 63.07
Granted | $ / shares 81.83
Vested | $ / shares 67.54
Forfeited | $ / shares 58.50
Unvested balance at end of period | $ / shares $ 73.45