Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax liabilities:
Property-related	$ 9,030	$ 13,094
Pension	364	454
Nuclear decommissioning trusts	226	253
Net unrealized gains on derivatives	263	581
Investments in partnerships and joint ventures	442	603
Other	871	1,272
Total deferred tax liabilities	11,196	16,257
Deferred tax assets and valuation allowance:
Decommissioning reserves	306	454
Postretirement benefits	74	145
Net operating loss carryforwards	482	427
Tax credit carryforwards	3,126	3,059
ARO and accrued asset removal costs	210	777
Deferred Tax Liabilities, Regulatory Assets	1,267	84
Other	646	940
Valuation allowance(b)	(252)	(269)
Net deferred tax assets	5,859	5,617
Net deferred income taxes	5,337	10,640
Deferred tax assets and liabilities included in the consolidated balance sheets [Abstract]
Noncurrent other assets	417	461
Deferred income taxes - noncurrent liabilities	(5,754)	(11,101)
Net deferred income taxes	(5,337)	(10,640)
FPL[Member]
Deferred tax liabilities:
Property-related	6,045	8,882
Pension	342	502
Nuclear decommissioning trusts	0	0
Net unrealized gains on derivatives	0	0
Investments in partnerships and joint ventures	0	0
Other	584	796
Total deferred tax liabilities	6,971	10,180
Deferred tax assets and valuation allowance:
Decommissioning reserves	271	401
Postretirement benefits	57	93
Net operating loss carryforwards	3	3
Tax credit carryforwards	0	0
ARO and accrued asset removal costs	146	699
Deferred Tax Liabilities, Regulatory Assets	1,273	84
Other	216	359
Valuation allowance(b)	0	0
Net deferred tax assets	1,966	1,639
Net deferred income taxes	5,005	8,541
Deferred tax assets and liabilities included in the consolidated balance sheets [Abstract]
Noncurrent other assets	0	0
Deferred income taxes - noncurrent liabilities	(5,005)	(8,541)
Net deferred income taxes	$ (5,005)	$ (8,541)