Income Taxes (Details Textuals) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Dec. 31, 2012
Income Taxes (Textuals) [Abstract]
Gross unrecognized tax benefits	$ 1,049			$ 1,052
Unrecognized tax benefits which would affect our effective tax rate, if recognized	913			902
Incremental tax liability asserted by IRS	1,162
Interest Expense Related To Income Taxes	9	2
Accrued Interest And Penalties Gross	378			364
Potential reduction in unrecognized tax benefits over next 12 months as a result of concluding certain matters			$ 15