Common Shareholders' Equity (Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Components Of Comprehensive Income And Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ (40)	$ 56
Other comprehensive income (loss) before reclassifications	(44)	(20)
Amounts reclassified from AOCI	8	(15)
Net other comprehensive income (loss)	(36)	(35)
Less other comprehensive loss attributable to noncontrolling interests	3
Ending balance	(73)	21
Net Unrealized Gains (Losses) on Cash Flow Hedges
Components Of Comprehensive Income And Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(156)	(115)
Other comprehensive income (loss) before reclassifications	(52)	(18)
Amounts reclassified from AOCI	18	9
Net other comprehensive income (loss)	(34)	(9)
Less other comprehensive loss attributable to noncontrolling interests	1
Ending balance	(189)	(124)
Net Unrealized Gains (Losses) on Available for Sale Securities
Components Of Comprehensive Income And Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	218	197
Other comprehensive income (loss) before reclassifications	12	13
Amounts reclassified from AOCI	(10)	(25)
Net other comprehensive income (loss)	2	(12)
Less other comprehensive loss attributable to noncontrolling interests	0
Ending balance	220	185
Defined Benefit Pension and Other Benefits Plans
Components Of Comprehensive Income And Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(20)	23
Other comprehensive income (loss) before reclassifications	(16)	4
Amounts reclassified from AOCI	0	1
Net other comprehensive income (loss)	(16)	5
Less other comprehensive loss attributable to noncontrolling interests	0
Ending balance	(36)	28
Net Unrealized Gains (Losses) on Foreign Currency Translation
Components Of Comprehensive Income And Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(58)	(33)
Other comprehensive income (loss) before reclassifications	14	(17)
Amounts reclassified from AOCI	0	0
Net other comprehensive income (loss)	14	(17)
Less other comprehensive loss attributable to noncontrolling interests	2
Ending balance	(42)	(50)
Other Comprehensive Loss Related to Equity Method Investee
Components Of Comprehensive Income And Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(24)	(16)
Other comprehensive income (loss) before reclassifications	(2)	(2)
Amounts reclassified from AOCI	0	0
Net other comprehensive income (loss)	(2)	(2)
Less other comprehensive loss attributable to noncontrolling interests	0
Ending balance	$ (26)	$ (18)