- Summary of Notes Payable (Parenthetical) (Detail) In Millions, unless otherwise specified	Sep. 30, 2013 3.45% senior notes due August 2015	Dec. 31, 2012 3.45% senior notes due August 2015	Sep. 30, 2013 2.65% senior notes due February 2017	Dec. 31, 2012 2.65% senior notes due February 2017	Sep. 30, 2013 8.50% senior notes due May 2019	Dec. 31, 2012 8.50% senior notes due May 2019	Sep. 30, 2013 4.00% senior notes due February 2022	Dec. 31, 2012 4.00% senior notes due February 2022	Sep. 30, 2013 3.625% senior notes due June 2023 USD ($)	Sep. 30, 2013 6.90% senior notes due December 2039	Dec. 31, 2012 6.90% senior notes due December 2039	Sep. 30, 2013 6.45% senior notes due August 2040	Dec. 31, 2012 6.45% senior notes due August 2040	Sep. 30, 2013 5.50% subordinated notes due September 2052	Dec. 31, 2012 5.50% subordinated notes due September 2052	Sep. 30, 2013 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Dec. 31, 2012 2.26% yen-denominated Uridashi notes due September 2016 JPY (¥)	Sep. 30, 2013 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 1.47% yen-denominated Samurai notes due July 2014 JPY (¥)	Sep. 30, 2013 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Dec. 31, 2012 1.84% yen-denominated Samurai notes due July 2016 JPY (¥)	Sep. 30, 2013 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Dec. 31, 2012 Variable interest rate yen-denominated Samurai notes due July 2014 JPY (¥)	Sep. 30, 2013 3.60% yen-denominated loan due July 2015 JPY (¥)	Dec. 31, 2012 3.60% yen-denominated loan due July 2015 JPY (¥)	Sep. 30, 2013 3.00% yen-denominated loan due August 2015 JPY (¥)	Dec. 31, 2012 3.00% yen-denominated loan due August 2015 JPY (¥)
Debt Instrument [Line Items]
Notes payable, interest rate	3.45%	3.45%	2.65%	2.65%	8.50%	8.50%	4.00%	4.00%	3.625%	6.90%	6.90%	6.45%	6.45%	5.50%	5.50%	2.26%	2.26%	1.47%	1.47%	1.84%	1.84%	1.31%	1.34%	3.60%	3.60%	3.00%	3.00%
Notes payable, principal amount									$ 700							¥ 8,000	¥ 8,000	¥ 28,700	¥ 28,700	¥ 15,800	¥ 15,800	¥ 5,500	¥ 5,500	¥ 10,000	¥ 10,000	¥ 5,000	¥ 5,000