Summary of Contractual Maturities of Cash Equivalent and Marketable Fixed Income Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Investments Classified by Contractual Maturity Date [Line Items]
Amortized Cost	$ 5,269
Estimated Fair Value	5,271
Due within one year
Investments Classified by Contractual Maturity Date [Line Items]
Amortized Cost	2,660
Estimated Fair Value	2,663
Due after one year through five years
Investments Classified by Contractual Maturity Date [Line Items]
Amortized Cost	2,175
Estimated Fair Value	2,175
Due After Five Years
Investments Classified by Contractual Maturity Date [Line Items]
Amortized Cost	434
Estimated Fair Value	$ 433