Stockholders' Equity Effect of Escrow Funding on the Company Repurchaseing its Common Stock (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended					12 Months Ended				12 Months Ended		1 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Jul. 31, 2012 Deposit into Litigation Escrow		Mar. 31, 2012 Deposit into Litigation Escrow	Dec. 31, 2011 Deposit into Litigation Escrow		Sep. 30, 2013 Class A common stock conversion_rate		Jul. 31, 2012 Class A common stock Deposit into Litigation Escrow	Dec. 31, 2011 Class A common stock Deposit into Litigation Escrow	Sep. 30, 2013 Class B common stock conversion_rate		Jul. 31, 2012 Class B common stock Deposit into Litigation Escrow	Dec. 31, 2011 Class B common stock Deposit into Litigation Escrow
Class of Stock [Line Items]
Deposits under the retrospective responsibility plan			$ 1,715	$ 150		$ 0	$ 1,565
Weighted-average repurchase price per share	$ 0		$ 0	$ 125.50	[1]		$ 101.75	[1]
Equivalent shares of class A common stock repurchased											1	15
Conversion rate after funding of class B common stock to class A common stock									0				0.4206		0.4206	0.4254
As-converted class B common stock outstanding aftetr deposits	638	[2]							508	[2]			103	[2]	103	104

[1] Effective price per share calculated using the volume-weighted average price of the Company's class A common stock over a pricing period in accordance with the Company's current certificate of incorporation.

[2] Figures in the table may not recalculate exactly due to rounding. As-converted class A common stock is calculated based on whole numbers, not the rounded numbers presented.