Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
	Apr. 12, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating activities [Abstract]
Net (loss) income			$ 77,041
Financing activities [Abstract]
Cash and cash equivalents at beginning of period			23,077
Cash and cash equivalents at end of period			6,127
Predecessor
Operating activities [Abstract]
Net (loss) income	$ (3,960)
Adjustments to reconcile net income (loss) to net cash provided by operating activities [Abstract]
Depreciation and amortization	45,869
Gain on sale of asset	(1,095)
Provision for doubtful accounts	1,212
Unearned compensation expense	3,276
Allowance for equity funds used during construction	(724)
Deferred income taxes	2,219
Deferred fuel costs	977
Cash surrender value of company-/trust-owned life insurance	(840)
Changes in assets and liabilities [Abstract]
Accounts receivable	(1,865)
Accounts receivable, affiliate	0
Unbilled revenue	563
Fuel inventory and materials and supplies	19,312
Prepayments	2,395
Accounts payable	8,348
Customer deposits	3,342
Provision for merger commitments	0
Postretirement benefit obligations	9,746
Regulatory assets and liabilities, net	5,178
Other deferred accounts	6,878
Taxes accrued	10,820
Interest accrued	17,909
Other operating	219
Net cash provided by operating activities	129,779
Investing activities [Abstract]
Additions to property, plant, and equipment	(42,392)
Allowance for equity funds used during construction	724
Proceeds from sale of property	1,932
Contributions to equity investment in investee	(2,450)
Return of equity investment in tax credit fund	476
Transfer of cash (to) from restricted accounts, net	4,847
Other investing	53
Net cash used in investing activities	(36,810)
Financing activities [Abstract]
Proceeds from short-term debt, net	0
Draws on credit facilities	3,000
Payments on credit facilities	(10,000)
Issuance of Long-term Debt	0
Repayment of long-term debt	(8,546)
Payment of Financing Costs	(43)
Dividends paid on common stock	(24,579)
Contributions from member/parent	0
Distributions to member/parent	0
Other financing	(717)
Net cash provided by (used in) financing activities	(40,885)
Net (decrease) increase in cash and cash equivalents	52,084
Cash and cash equivalents at beginning of period	68,246	$ 120,330		$ 68,246
Cash and cash equivalents at end of period	120,330
Supplementary cash flow information [Abstract]
Interest paid, net of amount capitalized	2,478
Income taxes paid (refunded), net	(481)
Supplementary non-cash investing and financing activities [Abstract]
Accrued additions to property, plant, and equipment	10,619
Non-cash additions to property, plant, and equipment	0
Successor
Operating activities [Abstract]
Net (loss) income		(42,294)	77,041
Adjustments to reconcile net income (loss) to net cash provided by operating activities [Abstract]
Depreciation and amortization		104,561	140,433
Gain on sale of asset		0	0
Provision for doubtful accounts		1,932	2,694
Unearned compensation expense		769	2,809
Allowance for equity funds used during construction		(2,056)	(4,446)
Deferred income taxes		(25,681)	41,192
Deferred fuel costs		(11,489)	4,231
Cash surrender value of company-/trust-owned life insurance		(2,198)	(3,940)
Changes in assets and liabilities [Abstract]
Accounts receivable		(23,157)	(44,139)
Accounts receivable, affiliate		(3,794)	12
Unbilled revenue		(13,643)	(4,643)
Fuel inventory and materials and supplies		19,464	(6,885)
Prepayments		(236)	5,509
Accounts payable		(15,294)	(22,325)
Customer deposits		5,421	9,317
Provision for merger commitments		40,357	(9,244)
Postretirement benefit obligations		2,267	3,789
Regulatory assets and liabilities, net		9,640	9,430
Other deferred accounts		(2,065)	(6,546)
Taxes accrued		5,006	22,233
Interest accrued		13,479	23,772
Other operating		5,714	6,595
Net cash provided by operating activities		66,703	246,889
Investing activities [Abstract]
Additions to property, plant, and equipment		(102,677)	(185,609)
Allowance for equity funds used during construction		2,056	4,446
Proceeds from sale of property		263	590
Contributions to equity investment in investee		0	0
Return of equity investment in tax credit fund		901	1,223
Transfer of cash (to) from restricted accounts, net		(33,943)	13,073
Other investing		137	7
Net cash used in investing activities		(133,263)	(166,270)
Financing activities [Abstract]
Proceeds from short-term debt, net		0	6,470
Draws on credit facilities		15,000	134,000
Payments on credit facilities		(15,000)	(134,000)
Issuance of Long-term Debt		1,350,000	0
Repayment of long-term debt		(1,358,268)	(17,896)
Payment of Financing Costs		(6,860)	(369)
Dividends paid on common stock		(572)	0
Contributions from member/parent		100,720	0
Distributions to member/parent		(56,000)	(83,955)
Other financing		(1,220)	(1,819)
Net cash provided by (used in) financing activities		27,800	(97,569)
Net (decrease) increase in cash and cash equivalents		(38,760)	(16,950)
Cash and cash equivalents at beginning of period		120,330	23,077
Cash and cash equivalents at end of period	120,330	81,570	6,127	81,570
Supplementary cash flow information [Abstract]
Interest paid, net of amount capitalized		42,963	64,555
Income taxes paid (refunded), net		256	(6)
Supplementary non-cash investing and financing activities [Abstract]
Accrued additions to property, plant, and equipment		15,853	13,083
Non-cash additions to property, plant, and equipment		0	3,015
Cleco Power [Member]
Operating activities [Abstract]
Net (loss) income			108,439	12,222
Adjustments to reconcile net income (loss) to net cash provided by operating activities [Abstract]
Depreciation and amortization			123,911	120,703
Gain on sale of asset			0	(1,095)
Provision for doubtful accounts			2,592	3,014
Unearned compensation expense			1,479	1,394
Allowance for equity funds used during construction			(4,446)	(2,780)
Deferred income taxes			12,847	5,201
Deferred fuel costs			4,231	(10,512)
Changes in assets and liabilities [Abstract]
Accounts receivable			(44,115)	(24,378)
Accounts receivable, affiliate			1,221	1,647
Unbilled revenue			(4,643)	(13,080)
Fuel inventory and materials and supplies			(6,885)	38,776
Prepayments			4,774	1,368
Accounts payable			(19,648)	(9,485)
Accounts payable, affiliate			611	(2,583)
Customer deposits			9,317	8,763
Provision for merger commitments			(9,244)	40,357
Postretirement benefit obligations			3,673	3,656
Regulatory assets and liabilities, net			7,939	13,893
Other deferred accounts			(6,093)	4,813
Taxes accrued			31,258	1,607
Interest accrued			13,207	15,147
Other operating			5,537	5,818
Net cash provided by operating activities			235,962	214,466
Investing activities [Abstract]
Additions to property, plant, and equipment			(183,604)	(144,637)
Allowance for equity funds used during construction			4,446	2,780
Proceeds from sale of property			590	2,195
Contributions to equity investment in investee			0	(2,450)
Transfer of cash (to) from restricted accounts, net			13,073	(29,096)
Other investing			637	190
Net cash used in investing activities			(164,858)	(171,018)
Financing activities [Abstract]
Proceeds from short-term debt, net			6,470	0
Draws on credit facilities			106,000	15,000
Payments on credit facilities			(106,000)	(15,000)
Repayment of long-term debt			(17,896)	(16,814)
Contributions from member/parent			0	50,000
Distributions to member/parent			(75,000)	(85,000)
Other financing			(1,933)	(2,070)
Net cash provided by (used in) financing activities			(88,359)	(53,884)
Net (decrease) increase in cash and cash equivalents			(17,255)	(10,436)
Cash and cash equivalents at beginning of period	$ 65,705		21,482	65,705
Cash and cash equivalents at end of period		$ 55,269	4,227	55,269
Supplementary cash flow information [Abstract]
Interest paid, net of amount capitalized			36,241	40,153
Income taxes paid (refunded), net			0	(485)
Supplementary non-cash investing and financing activities [Abstract]
Accrued additions to property, plant, and equipment			13,072	15,837
Non-cash additions to property, plant, and equipment			$ 3,015	$ 0