Percentage of Revenue by Geographic Area (Detail) - Geographic Concentration Risk - Total Revenue	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Concentration Risk [Line Items]
Revenues, percentage by country	100.00%	100.00%	100.00%
Sweden
Concentration Risk [Line Items]
Revenues, percentage by country	29.00%	37.00%	38.00%
United States
Concentration Risk [Line Items]
Revenues, percentage by country	39.00%	28.00%	33.00%
United Kingdom
Concentration Risk [Line Items]
Revenues, percentage by country	7.00%	17.00%	20.00%
Other
Concentration Risk [Line Items]
Revenues, percentage by country	25.00%	18.00%	9.00%