Accumulated Other Comprehensive Income (Loss) - After-tax Changes by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (3,279)	$ (3,777)	$ (3,422)	$ (3,778)
Amounts arising during the period	(232)	196	(137)	166
Reclassifications from accumulated other comprehensive income	16	58	64	89
Net other comprehensive income during the period	(216)	254	(73)	255
Balance at end of period	(3,495)	(3,523)	(3,495)	(3,523)
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(973)	(1,651)	(1,089)	(1,627)
Amounts arising during the period	(250)	231	(134)	207
Reclassifications from accumulated other comprehensive income	0	0	0	0
Net other comprehensive income during the period	(250)	231	(134)	207
Balance at end of period	(1,223)	(1,420)	(1,223)	(1,420)
Unrealized gains (losses) on qualifying derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(21)	(14)	(13)	(7)
Amounts arising during the period	19	(24)	(1)	(30)
Reclassifications from accumulated other comprehensive income	(19)	25	(7)	24
Net other comprehensive income during the period	0	1	(8)	(6)
Balance at end of period	(21)	(13)	(21)	(13)
Equity investees' AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	0	(1)	0	(1)
Amounts arising during the period	0	0	0	0
Reclassifications from accumulated other comprehensive income	0	1	0	1
Net other comprehensive income during the period	0	1	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)	(8)	(7)	(8)
Amounts arising during the period	(1)	0	(1)	0
Reclassifications from accumulated other comprehensive income	1	1	1	1
Net other comprehensive income during the period	0	1	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	(2,278)	(2,103)	(2,313)	(2,135)
Amounts arising during the period	0	(11)	(1)	(11)
Reclassifications from accumulated other comprehensive income	34	31	70	63
Net other comprehensive income during the period	34	20	69	52
Balance at end of period	(2,244)	(2,083)	(2,244)	(2,083)
LG And E And KU Energy LLC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(87)	(68)	(88)	(70)
Amounts arising during the period	1	(11)		(11)
Reclassifications from accumulated other comprehensive income	0	2	2	4
Net other comprehensive income during the period	1	(9)	2	(7)
Balance at end of period	(86)	(77)	(86)	(77)
LG And E And KU Energy LLC [Member] | Equity investees' AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	0	0	0	(1)
Amounts arising during the period	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
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	(9)	(8)	(9)	(8)
Amounts arising during the period	0	0		0
Reclassifications from accumulated other comprehensive income	1	1	1	1
Net other comprehensive income during the period	1	1	1	1
Balance at end of period	(8)	(7)	(8)	(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)	(60)	(79)	(61)
Amounts arising during the period	1	(11)		(11)
Reclassifications from accumulated other comprehensive income	(1)	1	1	2
Net other comprehensive income during the period	0	(10)	1	(9)
Balance at end of period	$ (78)	$ (70)	$ (78)	$ (70)