Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2017	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Unrecognized Tax Benefits	$ 1,058		$ 1,058			$ 1,056
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	902		902			900
Incremental tax liability asserted by IRS	$ 1,162		$ 1,162
Reported tax rate	47.80%	2.90%	97.00%	(86.90%)
Net tax expense/benefits related to interest and penalties	$ 13	$ 10	$ 23	$ 21
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 535		$ 535			$ 500
Subsequent Event [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Potential Reduction In Unrecognized Tax Benefits Over Next Twelve Months As Result Of Concluding Certain Matters					$ 767