Fair Value of Financial Assets and Liabilities - Fair Value Hierarchy For Financial Assets And Liabilities Measured At Fair Value (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	$ 14,284	$ 14,655
Investment in joint venture	38	37
Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	6,532	7,082
Investment in joint venture	0	0
Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	7,727	7,546
Investment in joint venture	0	0
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	25	27
Investment in joint venture	38	37
Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	1,643	2,022
Cash | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	1,643	2,022
Cash | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Cash | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	3,681	4,321
Cash equivalents | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	3,264	3,710
Cash equivalents | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	417	611
Cash equivalents | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
U.S. government and agency obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	2,380	1,951
U.S. government and agency obligations | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	1,404	1,141
U.S. government and agency obligations | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	976	810
U.S. government and agency obligations | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
U.S. corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	2,548	1,995
U.S. corporate debt securities | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
U.S. corporate debt securities | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	2,548	1,995
U.S. corporate debt securities | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
High yield corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	350	563
High yield corporate debt securities | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
High yield corporate debt securities | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	350	563
High yield corporate debt securities | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Asset-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	30	53
Asset-backed securities | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Asset-backed securities | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	30	53
Asset-backed securities | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	852	950
Municipal obligations | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Municipal obligations | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	852	950
Municipal obligations | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Auction rate securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	25	27
Auction rate securities | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Auction rate securities | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Auction rate securities | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	25	27
Foreign debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	2,554	2,564
Foreign debt securities | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Foreign debt securities | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	2,554	2,564
Foreign debt securities | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Publicly traded equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	221	209
Publicly traded equity securities | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	221	209
Publicly traded equity securities | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Publicly traded equity securities | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash and investments	0	0
Strategic investments held at cost
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost method strategic investments	382	333
Strategic investments held at cost | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost method strategic investments	0	0
Strategic investments held at cost | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost method strategic investments	0	0
Strategic investments held at cost | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost method strategic investments	382	333
Long-term debt carried at discounted cost
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt carried at discounted cost	(5,514)	(5,544)
Long-term debt carried at discounted cost | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt carried at discounted cost	0	0
Long-term debt carried at discounted cost | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt carried at discounted cost	(5,514)	(5,544)
Long-term debt carried at discounted cost | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt carried at discounted cost	0	0
Foreign Exchange Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets	49	44
Foreign exchange derivative liabilities	(47)	(71)
Foreign Exchange Contract | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets	0	0
Foreign exchange derivative liabilities	0	0
Foreign Exchange Contract | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets	49	44
Foreign exchange derivative liabilities	(47)	(71)
Foreign Exchange Contract | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets	0	0
Foreign exchange derivative liabilities	0	0
Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets		12
Foreign exchange derivative liabilities	(4)
Commodity Contract | Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets		0
Foreign exchange derivative liabilities	0
Commodity Contract | Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets		12
Foreign exchange derivative liabilities	(4)
Commodity Contract | Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign exchange derivative assets		$ 0
Foreign exchange derivative liabilities	$ 0