Equity (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (40)	$ (113)	$ (70)	$ (167)
Other comprehensive income (loss) before reclassifications	40	24	88	42
Amounts reclassified from AOCI	4	8	(3)	30
Total other comprehensive income, net of tax	44	32	85	72
Less other comprehensive income attributable to noncontrolling interests	1	1	12	(13)
Ending balance	3	(82)	3	(82)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(101)	(146)	(100)	(170)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI	5	13	14	36
Total other comprehensive income, net of tax	5	13	14	36
Less other comprehensive income attributable to noncontrolling interests	0	1	10	0
Ending balance	(96)	(134)	(96)	(134)
Net Unrealized Gains (Losses) on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	243	181	225	174
Other comprehensive income (loss) before reclassifications	26	17	60	25
Amounts reclassified from AOCI	(1)	(5)	(17)	(6)
Total other comprehensive income, net of tax	25	12	43	19
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	268	193	268	193
Defined Benefit Pension and Other Benefits Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(86)	(69)	(83)	(62)
Other comprehensive income (loss) before reclassifications	10	0	7	(7)
Amounts reclassified from AOCI	0	0	0	0
Total other comprehensive income, net of tax	10	0	7	(7)
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	(76)	(69)	(76)	(69)
Net Unrealized Gains (Losses) on Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(75)	(52)	(90)	(85)
Other comprehensive income (loss) before reclassifications	5	8	21	28
Amounts reclassified from AOCI	0	0	0	0
Total other comprehensive income, net of tax	5	8	21	28
Less other comprehensive income attributable to noncontrolling interests	1	0	2	(13)
Ending balance	(71)	(44)	(71)	(44)
Other Comprehensive Loss Related to Equity Method Investee
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(21)	(27)	(22)	(24)
Other comprehensive income (loss) before reclassifications	(1)	(1)	0	(4)
Amounts reclassified from AOCI	0	0	0	0
Total other comprehensive income, net of tax	(1)	(1)	0	(4)
Less other comprehensive income attributable to noncontrolling interests	0	0	0	0
Ending balance	$ (22)	$ (28)	$ (22)	$ (28)