Income Taxes (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Total UTB that, if recognized, would impact the effective income tax rate as of the end of the year	$ 50
Decrease of unrecognized tax benefit	60
State [Member]
Net operating loss carryforwards	80
Tax credit carryforward, amount	59
Loss carryforwards, charitable contribution	$ 119
Charitable Contribution Carryforward Expiration Date [Minimum]	Dec. 31, 2019
Charitable Contribution Carryforward Expiration Date [Maximum]	Dec. 31, 2020
Federal [Member]
Net operating loss carryforwards	$ 4,856
Capital loss carryforwards	29
Tax credit carryforward, amount	110
Loss carryforwards, charitable contribution	$ 178
Tax Credit Carryforward Expiration Date [Minimum]	Dec. 31, 2029
Tax Credit Carryforward Expiration Date [Maximum]	Dec. 31, 2035
Charitable Contribution Carryforward Expiration Date [Minimum]	Dec. 31, 2017
Charitable Contribution Carryforward Expiration Date [Maximum]	Dec. 31, 2020
Minimum [Member] | State [Member]
Tax credit carryforward expiration date	Dec. 31, 2033
Minimum [Member] | Federal [Member]
Tax credit carryforward expiration date	Dec. 31, 2029
Maximum [Member] | State [Member]
Tax credit carryforward expiration date	Dec. 31, 2034
Maximum [Member] | Federal [Member]
Tax credit carryforward expiration date	Dec. 31, 2035