Equity (Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (169)	$ (188)
Other comprehensive income (loss) before reclassifications	(43)	(35)
Amounts reclassified from AOCI	4	11
Total other comprehensive loss, net of tax	(39)	(24)
Impact of disposal of a business	10
Attributable to noncontrolling interests	(6)
Acquisition of Gulf Power		(1)
Balances, March 31, 2020	(198)
Ending balance	(192)	(213)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(27)	(55)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI	2	10
Total other comprehensive loss, net of tax	2	10
Impact of disposal of a business	23
Attributable to noncontrolling interests	0
Acquisition of Gulf Power		(1)
Balances, March 31, 2020	(2)
Ending balance	(2)	(46)
Net Unrealized Gains (Losses) on Available for Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	11	(7)
Other comprehensive income (loss) before reclassifications	(8)	8
Amounts reclassified from AOCI	(1)	2
Total other comprehensive loss, net of tax	(9)	10
Impact of disposal of a business	0
Attributable to noncontrolling interests	0
Acquisition of Gulf Power		0
Balances, March 31, 2020	2
Ending balance	2	3
Defined Benefit Pension and Other Benefits Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(114)	(65)
Other comprehensive income (loss) before reclassifications	0	(52)
Amounts reclassified from AOCI	3	(1)
Total other comprehensive loss, net of tax	3	(53)
Impact of disposal of a business	0
Attributable to noncontrolling interests	0
Acquisition of Gulf Power		0
Balances, March 31, 2020	(111)
Ending balance	(111)	(118)
Net Unrealized Gains (Losses) on Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(42)	(63)
Other comprehensive income (loss) before reclassifications	(35)	10
Amounts reclassified from AOCI	0	0
Total other comprehensive loss, net of tax	(35)	10
Impact of disposal of a business	(13)
Attributable to noncontrolling interests	(6)
Acquisition of Gulf Power		0
Balances, March 31, 2020	(90)
Ending balance	(84)	(53)
Other Comprehensive Income (Loss) Related to Equity Method Investees
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	3	2
Other comprehensive income (loss) before reclassifications	0	(1)
Amounts reclassified from AOCI	0	0
Total other comprehensive loss, net of tax	0	(1)
Impact of disposal of a business	0
Attributable to noncontrolling interests	0
Acquisition of Gulf Power		0
Balances, March 31, 2020	3
Ending balance	$ 3	$ 1