Business Segment Information - People's Republic of China Including Hong Kong Percentage Share of the Company's Total Revenue, Net Revenue, Total Identifiable Assets or Equity (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Total revenues | People's Republic of China, including Hong Kong
Concentration Risk [Line Items]
Concentration percentage	29.00%	31.00%	31.00%
Net revenues | People's Republic of China, including Hong Kong
Concentration Risk [Line Items]
Concentration percentage	18.00%	18.00%	18.00%
Identifiable assets at year end | People's Republic of China, including Hong Kong
Concentration Risk [Line Items]
Concentration percentage	14.00%	11.00%	15.00%
Equity | People's Republic of China, including Hong Kong
Concentration Risk [Line Items]
Concentration percentage	8.00%	8.00%	13.00%
Lower end | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration percentage	10.00%	10.00%	10.00%