Accumulated Other Comprehensive Income (Loss) - After-tax Changes by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ (3,523)	$ (2,857)	$ (3,778)	$ (2,728)
Amounts arising during the period	(14)	(585)	152	(784)
Reclassifications from accumulated other comprehensive income	34	(38)	123	32
Net other comprehensive income during the period	20	(623)	275	(752)
Balance at end of period	(3,503)	(3,480)	(3,503)	(3,480)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(1,420)	(716)	(1,627)	(520)
Amounts arising during the period	(12)	(641)	195	(837)
Reclassifications from accumulated other comprehensive income	0	0	0	0
Net other comprehensive income during the period	(12)	(641)	195	(837)
Balance at end of period	(1,432)	(1,357)	(1,432)	(1,357)
Qualifying Derivatives Unrealized Gains (Losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(13)	(5)	(7)	(7)
Amounts arising during the period	1	62	(29)	57
Reclassifications from accumulated other comprehensive income	0	(69)	24	(62)
Net other comprehensive income during the period	1	(7)	(5)	(5)
Balance at end of period	(12)	(12)	(12)	(12)
Equity Investees Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	0	(1)	(1)	0
Amounts arising during the period	0	0	0	0
Reclassifications from accumulated other comprehensive income	0	0	1	(1)
Net other comprehensive income during the period	0	0	1	(1)
Balance at end of period	0	(1)	0	(1)
Defined Benefit Plans Prior Service Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(7)	(5)	(8)	(6)
Amounts arising during the period	0	0	0	0
Reclassifications from accumulated other comprehensive income	0	0	1	1
Net other comprehensive income during the period	0	0	1	1
Balance at end of period	(7)	(5)	(7)	(5)
Defined Benefit Plans Actuarial Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(2,083)	(2,130)	(2,135)	(2,195)
Amounts arising during the period	(3)	(6)	(14)	(4)
Reclassifications from accumulated other comprehensive income	34	31	97	94
Net other comprehensive income during the period	31	25	83	90
Balance at end of period	(2,052)	(2,105)	(2,052)	(2,105)
LG And E And KU Energy LLC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(77)	(43)	(70)	(46)
Amounts arising during the period	(1)		(12)	1
Reclassifications from accumulated other comprehensive income	1	1	5	3
Net other comprehensive income during the period	0	1	(7)	4
Balance at end of period	(77)	(42)	(77)	(42)
LG And E And KU Energy LLC [Member] | Equity Investees Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	0	(1)	(1)	0
Amounts arising during the period	0		0	0
Reclassifications from accumulated other comprehensive income	0	0	1	(1)
Net other comprehensive income during the period	0	0	1	(1)
Balance at end of period	0	(1)	0	(1)
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	(7)	(9)	(8)	(10)
Amounts arising during the period	0		0	0
Reclassifications from accumulated other comprehensive income	0	0	1	1
Net other comprehensive income during the period	0	0	1	1
Balance at end of period	(7)	(9)	(7)	(9)
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	(70)	(33)	(61)	(36)
Amounts arising during the period	(1)		(12)	1
Reclassifications from accumulated other comprehensive income	1	1	3	3
Net other comprehensive income during the period	0	1	(9)	4
Balance at end of period	$ (70)	$ (32)	$ (70)	$ (32)