Accumulated Other Comprehensive Income (Loss) - After-tax Changes by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (3,495)	$ (3,523)	$ (3,422)	$ (3,778)
Amounts arising during the period	(173)	(14)	(310)	152
Reclassifications from accumulated other comprehensive income	20	34	84	123
Net other comprehensive income during the period	(153)	20	(226)	275
Balance at end of period	(3,648)	(3,503)	(3,648)	(3,503)
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(1,223)	(1,420)	(1,089)	(1,627)
Amounts arising during the period	(187)	(12)	(321)	195
Reclassifications from accumulated other comprehensive income	0	0	0	0
Net other comprehensive income during the period	(187)	(12)	(321)	195
Balance at end of period	(1,410)	(1,432)	(1,410)	(1,432)
Unrealized gains (losses) on qualifying derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(21)	(13)	(13)	(7)
Amounts arising during the period	22	1	21	(29)
Reclassifications from accumulated other comprehensive income	(14)	0	(21)	24
Net other comprehensive income during the period	8	1	0	(5)
Balance at end of period	(13)	(12)	(13)	(12)
Equity investees' AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	0	0	0	(1)
Amounts arising during the period	0	0	0	0
Reclassifications from accumulated other comprehensive income	0	0	0	1
Net other comprehensive income during the period	0	0	0	1
Balance at end of period	0	0	0	0
Defined benefit plans Prior service costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(7)	(7)	(7)	(8)
Amounts arising during the period	0	0	(1)	0
Reclassifications from accumulated other comprehensive income	0	0	1	1
Net other comprehensive income during the period	0	0	0	1
Balance at end of period	(7)	(7)	(7)	(7)
Defined benefit plans Actuarial gain (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(2,244)	(2,083)	(2,313)	(2,135)
Amounts arising during the period	(8)	(3)	(9)	(14)
Reclassifications from accumulated other comprehensive income	34	34	104	97
Net other comprehensive income during the period	26	31	95	83
Balance at end of period	(2,218)	(2,052)	(2,218)	(2,052)
LG And E And KU Energy LLC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(86)	(77)	(88)	(70)
Amounts arising during the period		(1)		(12)
Reclassifications from accumulated other comprehensive income	2	1	4	5
Net other comprehensive income during the period	2	0	4	(7)
Balance at end of period	(84)	(77)	(84)	(77)
LG And E And KU Energy LLC [Member] | Equity investees' AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	0	0	0	(1)
Amounts arising during the period		0		0
Reclassifications from accumulated other comprehensive income	0	0	0	1
Net other comprehensive income during the period	0	0	0	1
Balance at end of period	0	0	0	0
LG And E And KU Energy LLC [Member] | Defined benefit plans Prior service costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(8)	(7)	(9)	(8)
Amounts arising during the period		0		0
Reclassifications from accumulated other comprehensive income	1	0	2	1
Net other comprehensive income during the period	1	0	2	1
Balance at end of period	(7)	(7)	(7)	(7)
LG And E And KU Energy LLC [Member] | Defined benefit plans Actuarial gain (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(78)	(70)	(79)	(61)
Amounts arising during the period		(1)		(12)
Reclassifications from accumulated other comprehensive income	1	1	2	3
Net other comprehensive income during the period	1	0	2	(9)
Balance at end of period	$ (77)	$ (70)	$ (77)	$ (70)