Segments - Business Segment Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 1,572	$ 1,387	$ 4,655	$ 4,092
Depreciation and amortization	139	117	425	364
Restructuring charges	6	20	43	63
Stock-based compensation expense	12	11	35	32
Operating income/(loss)	313	244	784	626
Total assets	15,354		15,354		15,516
Operating Segment | Buy
Segment Reporting Information [Line Items]
Revenues	878	848	2,615	2,503
Depreciation and amortization	55	49	166	149
Restructuring charges	4	10	26	27
Stock-based compensation expense	3	3	12	10
Operating income/(loss)	109	107	252	268
Total assets	6,882		6,882		6,768
Operating Segment | Watch
Segment Reporting Information [Line Items]
Revenues	694	539	2,040	1,589
Depreciation and amortization	83	66	256	209
Restructuring charges	1	7	11	19
Stock-based compensation expense	2	3	8	7
Operating income/(loss)	226	163	602	441
Total assets	8,208		8,208		8,326
Corporate
Segment Reporting Information [Line Items]
Depreciation and amortization	1	2	3	6
Restructuring charges	1	3	6	17
Stock-based compensation expense	7	5	15	15
Operating income/(loss)	(22)	(26)	(70)	(83)
Total assets	$ 264		$ 264		$ 422