Income Taxes (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Total UTB that, if recognized, would impact the effective income tax rate as of the end of the year	$ 25
Decrease of unrecognized tax benefit	70
State [Member]
Net operating loss carryforwards	0
Tax credit carryforward, amount	51
Loss carryforwards, charitable contribution	$ 112
Charitable Contribution Carryforward Expiration Date [Minimum]	Dec. 31, 2019
Charitable Contribution Carryforward Expiration Date [Maximum]	Dec. 31, 2021
Federal [Member]
Net operating loss carryforwards	$ 5,009
Tax credit carryforward, amount	116
Loss carryforwards, charitable contribution	$ 192
Tax Credit Carryforward Expiration Date [Minimum]	Dec. 31, 2029
Tax Credit Carryforward Expiration Date [Maximum]	Dec. 31, 2036
Charitable Contribution Carryforward Expiration Date [Minimum]	Dec. 31, 2017
Charitable Contribution Carryforward Expiration Date [Maximum]	Dec. 31, 2021
Minimum [Member] | State [Member]
Tax credit carryforward expiration date
Minimum [Member] | Federal [Member]
Tax credit carryforward expiration date	Dec. 31, 2029
Maximum [Member] | State [Member]
Tax credit carryforward expiration date
Maximum [Member] | Federal [Member]
Tax credit carryforward expiration date	Dec. 31, 2036