XML 127 R108.htm IDEA: XBRL DOCUMENT v3.8.0.1
Treasury Stock - Additional Information (Detail) - shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Schedule of Capitalization, Equity [Line Items]      
Share Repurchase Plan, shares repurchased (in shares) 20,690,892 4,893,150 0
American Depository Shares      
Schedule of Capitalization, Equity [Line Items]      
Share Repurchase Plan, shares repurchased (in shares) 3,448,482 815,525 0
Business acquisition, shares issued 0 223,161 146,372