Common Shareholders' Equity (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (113)	$ (73)	$ (167)	$ (40)
Other comprehensive income (loss) before reclassifications	24	51	42	8
Amounts reclassified from AOCI	8	19	30	26
Net other comprehensive income (loss)	32	70	72	34
Less other comprehensive income attributable to noncontrolling interests	1	1	(13)	(2)
Ending balance	(82)	(4)	(82)	(4)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(146)	(189)	(170)	(156)
Other comprehensive income (loss) before reclassifications	0	40	0	(11)
Amounts reclassified from AOCI	13	22	36	39
Net other comprehensive income (loss)	13	62	36	28
Less other comprehensive income attributable to noncontrolling interests	1	1	0	0
Ending balance	(134)	(128)	(134)	(128)
Net Unrealized Gains (Losses) on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	181	220	174	218
Other comprehensive income (loss) before reclassifications	17	(7)	25	5
Amounts reclassified from AOCI	(5)	(3)	(6)	(13)
Net other comprehensive income (loss)	12	(10)	19	(8)
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	193	210	193	210
Defined Benefit Pension and Other Benefits Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(69)	(36)	(62)	(20)
Other comprehensive income (loss) before reclassifications	0	0	(7)	(16)
Amounts reclassified from AOCI	0	0	0	0
Net other comprehensive income (loss)	0	0	(7)	(16)
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	(69)	(36)	(69)	(36)
Net Unrealized Gains (Losses) on Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(52)	(42)	(85)	(58)
Other comprehensive income (loss) before reclassifications	8	15	28	29
Amounts reclassified from AOCI	0	0	0	0
Net other comprehensive income (loss)	8	15	28	29
Less other comprehensive income attributable to noncontrolling interests	0	0	(13)	(2)
Ending balance	(44)	(27)	(44)	(27)
Other Comprehensive Income (Loss) Related to Equity Method Investee
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(27)	(26)	(24)	(24)
Other comprehensive income (loss) before reclassifications	(1)	3	(4)	1
Amounts reclassified from AOCI	0	0	0	0
Net other comprehensive income (loss)	(1)	3	(4)	1
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	$ (28)	$ (23)	$ (28)	$ (23)