Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 12, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Activities [Abstract]
Cash and cash equivalents at beginning of period	$ 68,246		$ 23,077	$ 68,246
Cash and cash equivalents at end of period		$ 23,077	119,040	23,077	$ 68,246
Successor [Member]
Operating Activities [Abstract]
Net income (loss)		(24,113)	138,080
Adjustments to reconcile net income (loss) to net cash provided by operating activities [Abstract]
Depreciation and amortization		141,544	186,326
Gain on sale of assets		0	(2)
Provision for doubtful accounts		4,473	2,778
Unearned compensation expense		1,147	3,745
Allowance for equity funds used during construction		(3,735)	(8,320)
Deferred income taxes		(21,053)	(41,966)
Deferred fuel costs		(8,192)	11,909
Cash surrender value of company-/trust-owned life insurance		(2,561)	(5,892)
Changes in assets and liabilities [Abstract]
Accounts receivable		(21,537)	(25,584)
Unbilled revenue		(837)	(2,129)
Fuel inventory and materials and supplies		2,880	(44,995)
Prepayments		(2,514)	2,852
Accounts payable		5,183	14,705
Customer deposits		7,333	12,381
Provision for merger commitments		21,964	(12,971)
Postretirement benefit obligations		3,750	4,884
Regulatory assets and liabilities, net		13,750	12,531
Other deferred accounts		(28,010)	(8,380)
Taxes accrued		(24,210)	23,118
Interest accrued		(11,104)	(582)
Deferred compensation		(799)	308
Other operating		(2,037)	2,632
Net cash provided by operating activities		51,322	265,428
Investing Activities [Abstract]
Additions to property, plant, and equipment		(144,444)	(236,932)
Allowance for equity funds used during construction		3,735	8,320
Proceeds from sale of property, plant, and equipment		766	17,499
Reimbursement for property loss		3,159	187
Contributions to equity investment in investee		0	0
Premiums paid on trust-owned life insurance		0	0
Return of equity investment in tax credit fund		901	7,502
Contributions to tax credit fund		0	(630)
Transfer of cash (to) from restricted accounts, net		(25,884)	13,332
Other investing		622	500
Net cash (used in) provided by investing activities		(161,145)	(190,222)
Financing Activities [Abstract]
Draws on credit facility		15,000	179,000
Payments on credit facility		(15,000)	(179,000)
Issuance of long-term debt		1,680,000	125,000
Repayment of long-term debt		(1,668,268)	(17,896)
Payments of financing costs		(8,655)	(463)
Dividends paid on common stock		(572)	0
Contribution from parent/member		100,720	0
Distributions to parent/member		(88,765)	(84,065)
Other financing		(1,890)	(1,819)
Net cash provided by (used in) financing activities		12,570	20,757
Net increase (decrease) in cash and cash equivalents		(97,253)	95,963
Cash and cash equivalents at beginning of period		120,330	23,077
Cash and cash equivalents at end of period	120,330	23,077	119,040	23,077
Supplementary cash flow information [Abstract]
Interest paid, net of amount capitalized		116,496	118,009
Income taxes (refunded) paid, net		4,263	(6)
Supplementary non-cash investing and financing activities [Abstract]
Accrued additions to property, plant, and equipment		17,599	31,083
Non-cash additions to property, plant, and equipment		0	3,015
Predecessor [Member]
Operating Activities [Abstract]
Net income (loss)	(3,960)				133,669
Adjustments to reconcile net income (loss) to net cash provided by operating activities [Abstract]
Depreciation and amortization	45,869				156,211
Gain on sale of assets	(1,095)				0
Provision for doubtful accounts	1,212				3,464
Unearned compensation expense	3,276				6,344
Allowance for equity funds used during construction	(723)				(3,063)
Deferred income taxes	2,219				74,103
Deferred fuel costs	977				9,899
Cash surrender value of company-/trust-owned life insurance	(840)				950
Changes in assets and liabilities [Abstract]
Accounts receivable	(1,865)				(13,656)
Unbilled revenue	563				4,481
Fuel inventory and materials and supplies	19,312				(13,698)
Prepayments	2,395				2,750
Accounts payable	8,348				(25,294)
Customer deposits	3,342				12,162
Provision for merger commitments	0				0
Postretirement benefit obligations	9,746				14,173
Regulatory assets and liabilities, net	5,178				18,793
Other deferred accounts	6,878				(17,454)
Taxes accrued	10,820				(831)
Interest accrued	17,909				(1,024)
Deferred compensation	(793)				(1,166)
Other operating	1,012				209
Net cash provided by operating activities	129,780				361,022
Investing Activities [Abstract]
Additions to property, plant, and equipment	(42,392)				(156,819)
Allowance for equity funds used during construction	723				3,063
Proceeds from sale of property, plant, and equipment	1,932				0
Reimbursement for property loss	53				0
Contributions to equity investment in investee	(2,450)				(2,290)
Premiums paid on trust-owned life insurance	0				(3,607)
Return of equity investment in tax credit fund	476				2,128
Contributions to tax credit fund	0				(9,966)
Transfer of cash (to) from restricted accounts, net	4,847				(1,341)
Other investing	0				881
Net cash (used in) provided by investing activities	(36,811)				(167,951)
Financing Activities [Abstract]
Draws on credit facility	3,000				120,000
Payments on credit facility	(10,000)				(163,000)
Issuance of long-term debt	0				75,000
Repayment of long-term debt	(8,546)				(100,824)
Payments of financing costs	(43)				(693)
Dividends paid on common stock	(24,579)				(97,283)
Contribution from parent/member	0				0
Distributions to parent/member	0				0
Other financing	(717)				(2,448)
Net cash provided by (used in) financing activities	(40,885)				(169,248)
Net increase (decrease) in cash and cash equivalents	52,084				23,823
Cash and cash equivalents at beginning of period	68,246	120,330		68,246	44,423
Cash and cash equivalents at end of period	120,330				68,246
Supplementary cash flow information [Abstract]
Interest paid, net of amount capitalized	2,478				74,349
Income taxes (refunded) paid, net	(481)				1,434
Supplementary non-cash investing and financing activities [Abstract]
Accrued additions to property, plant, and equipment	10,619				7,313
Non-cash additions to property, plant, and equipment	0				184
Cleco Power [Member]
Operating Activities [Abstract]
Net income (loss)			150,738	39,128	141,350
Adjustments to reconcile net income (loss) to net cash provided by operating activities [Abstract]
Depreciation and amortization			165,200	152,978	152,833
Gain on sale of assets			0	(1,095)	0
Provision for doubtful accounts			2,677	5,512	2,986
Unearned compensation expense			1,972	1,572	2,000
Allowance for equity funds used during construction			(8,320)	(4,458)	(3,063)
Deferred income taxes			(34,191)	20,492	43,675
Deferred fuel costs			11,909	(7,215)	9,899
Changes in assets and liabilities [Abstract]
Accounts receivable			(25,696)	(23,306)	(13,681)
Accounts receivable, affiliate			1,865	2,612	6,195
Unbilled revenue			(2,129)	(274)	4,481
Fuel inventory and materials and supplies			(44,995)	22,192	(13,698)
Prepayments			2,745	228	1,323
Accounts payable			11,005	9,140	(20,575)
Accounts payable, affiliate			1,349	(3,639)	(3,990)
Customer deposits			12,381	10,675	12,162
Provision for merger commitments			(12,971)	21,964	0
Postretirement benefit obligations			4,849	5,076	7,405
Regulatory assets and liabilities, net			10,544	17,506	18,793
Other deferred accounts			(8,137)	(21,818)	(15,991)
Taxes accrued			44,101	(29,535)	36,287
Interest accrued			(59)	(671)	(1,412)
Other operating			2,241	(1,307)	(441)
Net cash provided by operating activities			287,078	215,757	366,538
Investing Activities [Abstract]
Additions to property, plant, and equipment			(235,252)	(186,143)	(156,357)
Allowance for equity funds used during construction			8,320	4,458	3,063
Proceeds from sale of property, plant, and equipment			4,078	2,698	0
Reimbursement for property loss			187	3,212	0
Contributions to equity investment in investee			0	(2,450)	(2,290)
Transfer of cash (to) from restricted accounts, net			13,332	(21,037)	(1,341)
Other investing			500	622	881
Net cash (used in) provided by investing activities			(208,835)	(198,640)	(156,044)
Financing Activities [Abstract]
Draws on credit facility			106,000	15,000	63,000
Payments on credit facility			(106,000)	(15,000)	(83,000)
Issuance of long-term debt			125,000	330,000	75,000
Repayment of long-term debt			(17,896)	(326,814)	(100,824)
Contribution from parent/member			0	50,000	0
Distributions to parent/member			(135,000)	(110,000)	(135,000)
Other financing			(2,013)	(4,526)	(3,127)
Net cash provided by (used in) financing activities			(29,909)	(61,340)	(183,951)
Net increase (decrease) in cash and cash equivalents			48,334	(44,223)	26,543
Cash and cash equivalents at beginning of period	$ 65,705		21,482	65,705	39,162
Cash and cash equivalents at end of period		$ 21,482	69,816	21,482	65,705
Supplementary cash flow information [Abstract]
Interest paid, net of amount capitalized			65,984	92,585	74,219
Income taxes (refunded) paid, net			0	(485)	(27)
Supplementary non-cash investing and financing activities [Abstract]
Accrued additions to property, plant, and equipment			30,883	16,755	7,249
Non-cash additions to property, plant, and equipment			$ 3,015	$ 0	$ 184