Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value of Financial Instruments
Short-term investments	$ 121		$ 121		$ 34
Total long-term debt	27,200		27,200
Estimated fair value of long-term debt	28,500		28,500
Related Party Transaction, Amounts of Transaction	16	$ 7	37	$ 34
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets	1,476		1,476		1,445
Assets	92,362		92,362		74,187
Long-term debt	26,771		26,771		11,630
Total liabilities and shareholders’ equity	$ 92,362		$ 92,362		74,187
Long-term Debt [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reductions in Other Assets and Long-Term Debt, Amount					65
Other noncurrent assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reductions in Other Assets and Long-Term Debt, Amount					65
Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets					(65)
Assets					(65)
Long-term debt					(65)
Total liabilities and shareholders’ equity					(65)
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets					1,510
Assets					74,252
Long-term debt					11,695
Total liabilities and shareholders’ equity					$ 74,252