Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Apr. 12, 2016	Dec. 31, 2016		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning				$ 2,096,357
Other comprehensive income before reclassifications
Balance, ending				2,124,740	$ 2,096,357
PREDECESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	$ 1,674,841					$ 1,674,841
Other comprehensive income before reclassifications
Balance, ending	1,646,061
SUCCESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning		$ 2,158,141	[1]	2,096,357	2,046,763
Other comprehensive income before reclassifications
Postretirement benefit adjustments incurred during the year		2,304		3,681	(3,898)
Reclassification of effect of tax rate change				(589)
Balance, ending		2,046,763		2,124,740	2,096,357	2,046,763
CLECO POWER
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	1,552,404			1,550,679	1,535,202	1,552,404
Other comprehensive income before reclassifications
Postretirement benefit adjustments incurred during the year				954	(948)	3,913
Reclassification of effect of tax rate change				(2,496)
Balance, ending		1,535,202		1,594,533	1,550,679	1,535,202
POSTRETIREMENT BENEFIT NET (LOSS) GAIN | PREDECESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	(20,857)					(20,857)
Other comprehensive income before reclassifications
Amounts reclassified from accumulated other comprehensive loss/income	587
Balance, ending	(20,270)
POSTRETIREMENT BENEFIT NET (LOSS) GAIN | SUCCESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning				(2,921)	1,500
Other comprehensive income before reclassifications
Postretirement benefit adjustments incurred during the year		2,304		3,681	(3,898)
Amounts reclassified from accumulated other comprehensive loss/income		(804)		1,615	(523)
Balance, ending	0	1,500		1,786	(2,921)	1,500
POSTRETIREMENT BENEFIT NET (LOSS) GAIN | CLECO POWER
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	(11,364)			(8,377)	(7,905)	(11,364)
Other comprehensive income before reclassifications
Postretirement benefit adjustments incurred during the year				954	(948)	3,913
Amounts reclassified from accumulated other comprehensive loss/income				1,789	476	(454)
Reclassification of effect of tax rate change				(1,426)
Balance, ending		(7,905)		(7,060)	(8,377)	(7,905)
NET (LOSS) GAIN ON CASH FLOW HEDGES | PREDECESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	(5,728)					(5,728)
Other comprehensive income before reclassifications
Amounts reclassified from accumulated other comprehensive loss/income	60
Balance, ending	(5,668)
NET (LOSS) GAIN ON CASH FLOW HEDGES | SUCCESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning				0	0
Other comprehensive income before reclassifications
Balance, ending	0	0		0	0	0
NET (LOSS) GAIN ON CASH FLOW HEDGES | CLECO POWER
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	(5,728)			(5,306)	(5,517)	(5,728)
Other comprehensive income before reclassifications
Amounts reclassified from accumulated other comprehensive loss/income				254	211	211
Reclassification of effect of tax rate change				(1,070)
Balance, ending		(5,517)		(6,122)	(5,306)	(5,517)
TOTAL AOCI
Other comprehensive income before reclassifications
Reclassification of effect of tax rate change				(600)
TOTAL AOCI | PREDECESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	(26,585)					(26,585)
Other comprehensive income before reclassifications
Balance, ending	(25,938)
TOTAL AOCI | SUCCESSOR
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning		0	[1]	(2,921)	1,500
Other comprehensive income before reclassifications
Reclassification of effect of tax rate change				(589)
Balance, ending	0	1,500		1,786	(2,921)	1,500
TOTAL AOCI | CLECO POWER
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning	$ (17,092)			(13,683)	(13,422)	(17,092)
Other comprehensive income before reclassifications
Reclassification of effect of tax rate change				(2,500)
Balance, ending		$ (13,422)		$ (13,182)	$ (13,683)	$ (13,422)

[1] The April 13, 2016, beginning balance of the successor company differs from the April 12, 2016, ending balances of the predecessor company due to acquisition accounting adjustments related to the 2016 Merger.