Common Shareholders' Equity (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning	$ (40)	$ 56	$ (255)
Other comprehensive income (loss) before reclassifications	(164)	(156)	259
Amounts reclassified from AOCI	26	58	52
Total other comprehensive income (loss), net of tax	(138)	(98)	311
Less other comprehensive loss attributable to noncontrolling interests	(11)	(2)
Accumulated other comprehensive loss, ending	(167)	(40)	56
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning	(156)	(115)	(266)
Other comprehensive income (loss) before reclassifications	(88)	(141)	84
Amounts reclassified from AOCI	63	98	67
Total other comprehensive income (loss), net of tax	(25)	(43)	151
Less other comprehensive loss attributable to noncontrolling interests	(11)	(2)
Accumulated other comprehensive loss, ending	(170)	(156)	(115)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning	218	197	96
Other comprehensive income (loss) before reclassifications	(7)	62	118
Amounts reclassified from AOCI	(37)	(41)	(17)
Total other comprehensive income (loss), net of tax	(44)	21	101
Less other comprehensive loss attributable to noncontrolling interests	0	0
Accumulated other comprehensive loss, ending	174	218	197
Accumulated Defined Benefit Plans Adjustment [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning	(20)	23	(74)
Other comprehensive income (loss) before reclassifications	(42)	(44)	95
Amounts reclassified from AOCI	0	1	2
Total other comprehensive income (loss), net of tax	(42)	(43)	97
Less other comprehensive loss attributable to noncontrolling interests	0	0
Accumulated other comprehensive loss, ending	(62)	(20)	23
Accumulated Translation Adjustment [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning	(58)	(33)	12
Other comprehensive income (loss) before reclassifications	(27)	(25)	(45)
Amounts reclassified from AOCI	0	0	0
Total other comprehensive income (loss), net of tax	(27)	(25)	(45)
Less other comprehensive loss attributable to noncontrolling interests	0	0
Accumulated other comprehensive loss, ending	(85)	(58)	(33)
Accumulated Income (Loss) Related to Equity Method Investee [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning	(24)
Less other comprehensive loss attributable to noncontrolling interests	0	0
Accumulated other comprehensive loss, ending	(24)	(24)
Other ComprehesiveIncomeEquityMethod [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning		(16)	(23)
Other comprehensive income (loss) before reclassifications	0	(8)	7
Amounts reclassified from AOCI	0	0	0
Total other comprehensive income (loss), net of tax	$ 0	$ (8)	7
Accumulated other comprehensive loss, ending			$ (16)