Equity (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 3	$ (82)	$ (70)	$ (167)
Other comprehensive income before reclassifications	42	25	129	67
Amounts reclassified from AOCI	3	15	0	45
Total other comprehensive income, net of tax	45	40	129	112
Less other comprehensive income attributable to noncontrolling interests	0	(6)	11	(19)
Ending balance	48	(36)	48	(36)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(96)	(134)	(100)	(170)
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from AOCI	10	17	24	53
Total other comprehensive income, net of tax	10	17	24	53
Less other comprehensive income attributable to noncontrolling interests	(1)	0	9	0
Ending balance	(85)	(117)	(85)	(117)
Net Unrealized Gains (Losses) on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	268	193	225	174
Other comprehensive income before reclassifications	31	31	91	56
Amounts reclassified from AOCI	(6)	(2)	(23)	(8)
Total other comprehensive income, net of tax	25	29	68	48
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	293	222	293	222
Defined Benefit Pension and Other Benefits Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(76)	(69)	(83)	(62)
Other comprehensive income before reclassifications	0	0	7	(7)
Amounts reclassified from AOCI	(1)	0	(1)	0
Total other comprehensive income, net of tax	(1)	0	6	(7)
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	(77)	(69)	(77)	(69)
Net Unrealized Gains (Losses) on Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(71)	(44)	(90)	(85)
Other comprehensive income before reclassifications	10	(9)	30	19
Amounts reclassified from AOCI	0	0	0	0
Total other comprehensive income, net of tax	10	(9)	30	19
Less other comprehensive income attributable to noncontrolling interests	1	(6)	2	(19)
Ending balance	(62)	(47)	(62)	(47)
Other Comprehensive Income (Loss) Related to Equity Method Investee
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(22)	(28)	(22)	(24)
Other comprehensive income before reclassifications	1	3	1	(1)
Amounts reclassified from AOCI	0	0	0	0
Total other comprehensive income, net of tax	1	3	1	(1)
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	$ (21)	$ (25)	$ (21)	$ (25)