Debt and Interest Expense - Outstanding Debt Table (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Debt Disclosure [Abstract]
Total debt at face value	$ 15,202		$ 15,202
Net unamortized discounts and premiums (1)	(1,641)	[1]	(1,645)	[1]
Total borrowings	13,561		13,557
Capital lease obligation	8		8
Less current portion of long-term debt	0		500
Total long-term debt	$ 13,569		$ 13,065

[1] Unamortized discounts and premiums are amortized over the term of the related debt.