Income Taxes - Additional Information (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Unrecognized tax benefit, affect the effective tax rate	$ 332	$ 314
Accruals for payment of interest and penalties associated with uncertain tax positions	182	159
Net deferred tax is a combination of deferred tax liabilities and valuation allwance	1,400	905
Tax Reserve	270
Accrued interest expenses to recognize the estimated tax exposure	$ 150