Income Taxes Operating Loss and Tax Credit Carryforwards, United States, By Expiration Dates (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
2012 through 2016 [Member]
Operating Loss and Tax Credit Carry Forward [Line Items]
United States federal income tax loss carryforwards	$ 3
United States federal deferred income tax assets for income tax loss carryforwards	1
United States federal income tax credit carryforwards	0
2017 through 2021 [Member]
Operating Loss and Tax Credit Carry Forward [Line Items]
United States federal income tax loss carryforwards	0
United States federal deferred income tax assets for income tax loss carryforwards	0
United States federal income tax credit carryforwards	93
2022 through 2026 [Member]
Operating Loss and Tax Credit Carry Forward [Line Items]
United States federal income tax loss carryforwards	14
United States federal deferred income tax assets for income tax loss carryforwards	5
United States federal income tax credit carryforwards	20
2027 through 2031 [Member]
Operating Loss and Tax Credit Carry Forward [Line Items]
United States federal income tax loss carryforwards	3
United States federal deferred income tax assets for income tax loss carryforwards	1
United States federal income tax credit carryforwards	86
Not subject to expiration [Member]
Operating Loss and Tax Credit Carry Forward [Line Items]
United States federal income tax loss carryforwards	0
United States federal deferred income tax assets for income tax loss carryforwards	0
United States federal income tax credit carryforwards	52
Valuation allowance [Member]
Operating Loss and Tax Credit Carry Forward [Line Items]
United States federal income tax loss carryforwards	0
United States federal deferred income tax assets for income tax loss carryforwards	(6)
United States federal income tax credit carryforwards	$ (17)