Common Shareholders' Equity (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (167)	$ (40)
Other comprehensive Income (loss) before reclassifications	18	(44)
Amounts reclassified from AOCI	22	8
Net other comprehensive income (loss)	40	(36)
Less other comprehensive loss attributable to noncontrolling interests	(14)	(3)
Ending balance	(113)	(73)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(170)	(156)
Other comprehensive Income (loss) before reclassifications	0	(52)
Amounts reclassified from AOCI	23	18
Net other comprehensive income (loss)	23	(34)
Less other comprehensive loss attributable to noncontrolling interests	(1)	(1)
Ending balance	(146)	(189)
Net Unrealized Gains (Losses) on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	174	218
Other comprehensive Income (loss) before reclassifications	8	12
Amounts reclassified from AOCI	(1)	(10)
Net other comprehensive income (loss)	7	2
Less other comprehensive loss attributable to noncontrolling interests	0	0
Ending balance	181	220
Defined Benefit Pension and Other Benefits Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(62)	(20)
Other comprehensive Income (loss) before reclassifications	(7)	(16)
Amounts reclassified from AOCI	0	0
Net other comprehensive income (loss)	(7)	(16)
Less other comprehensive loss attributable to noncontrolling interests	0	0
Ending balance	(69)	(36)
Net Unrealized Gains (Losses) on Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(85)	(58)
Other comprehensive Income (loss) before reclassifications	20	14
Amounts reclassified from AOCI	0	0
Net other comprehensive income (loss)	20	14
Less other comprehensive loss attributable to noncontrolling interests	(13)	(2)
Ending balance	(52)	(42)
Other Comprehensive Income (Loss) Related to Equity Method Investee
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(24)	(24)
Other comprehensive Income (loss) before reclassifications	(3)	(2)
Amounts reclassified from AOCI	0	0
Net other comprehensive income (loss)	(3)	(2)
Less other comprehensive loss attributable to noncontrolling interests	0	0
Ending balance	$ (27)	$ (26)