Segment Information Segment reporting information, revenue for reportable segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue from External Customer [Line Items]
Product sales	$ 8,126	$ 6,413	$ 15,531	$ 11,284
Total antiviral products
Revenue from External Customer [Line Items]
Product sales	7,631	6,012	14,619	10,521
Harvoni
Revenue from External Customer [Line Items]
Product sales	3,608	0	7,187	0
Sovaldi
Revenue from External Customer [Line Items]
Product sales	1,291	3,481	2,263	5,755
Truvada
Revenue from External Customer [Line Items]
Product sales	849	806	1,620	1,566
Atripla
Revenue from External Customer [Line Items]
Product sales	782	870	1,516	1,650
Stribild
Revenue from External Customer [Line Items]
Product sales	447	270	803	485
Complera/Eviplera
Revenue from External Customer [Line Items]
Product sales	367	299	687	550
Viread
Revenue from External Customer [Line Items]
Product sales	271	261	505	472
Other antiviral
Revenue from External Customer [Line Items]
Product sales	16	25	38	43
Letairis
Revenue from External Customer [Line Items]
Product sales	176	145	327	268
Ranexa
Revenue from External Customer [Line Items]
Product sales	141	123	258	234
AmBisome
Revenue from External Customer [Line Items]
Product sales	103	94	188	186
Zydelig
Revenue from External Customer [Line Items]
Product sales	30	0	56	0
Other
Revenue from External Customer [Line Items]
Product sales	$ 45	$ 39	$ 83	$ 75