Summary of Significant Accounting Policies (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Loss
Unamortized benefit plan costs, net of tax benefit of $3,149 in 2012 and $2,289 in 2011	$ (4,790,000,000)	$ (3,487,000,000)
Cumulative translation adjustment	4,000,000	(4,000,000)
Net unrealized (loss) gain on marketable securities and cash flow hedges, net of tax expense of $0 in both 2012 and 2011	(1,000,000)	1,000,000
Total accumulated other comprehensive loss	(4,787,000,000)	(3,490,000,000)
Unamortized (gain) loss arising during period, tax	(3,149,000,000)	(2,289,000,000)
Net unrealized gain on marketable securities and cash flow hedges, tax	0	0
Change in unamortized benefit plan costs, net of tax	1,303,000,000	1,249,000,000	(297,000,000)
Net After Tax Actuarial Loss Amounts	$ 5,100,000,000	$ 3,900,000,000
Percentage Threshold Net Actuarial Gains Losses Subject To Amortization	10.00%
Average future service period of employees	10 years