Fair Value Accounting - Fair Value Measurements and Disclosures (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) $ / MW	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) $ / MW	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) $ / MW
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
FTR forward price - per MWh, low | $ / MW	(3.84)		(3.84)		(2.95)
FTR forward price - per MWh, high | $ / MW	7.42		7.42		6.33
Fair value, concentration of risk, amount of money market funds in cash and cash equivalents	$ 112,500,000		$ 112,500,000		$ 111,100,000
Fair value, assets and liabilities, transfers between levels, amount	0		0		0
Restricted Cash and Cash Equivalents, Current
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	9,900,000		9,900,000		13,100,000
Restricted Cash and Cash Equivalents, Noncurrent
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	18,900,000		18,900,000		20,100,000
Measured On A Recurring Basis
Asset description
Institutional money market funds	141,290,000		141,290,000		144,302,000
FTRs	26,077,000		26,077,000		7,396,000
Total assets	167,367,000		167,367,000		151,698,000
Liability description
FTRs	944,000		944,000		352,000
Total liabilities	944,000		944,000		352,000
Price Risk Derivative
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	4,283,000	$ 4,418,000	7,044,000	$ 7,683,000
Unrealized gains (losses)	2,420,000	(2,460,000)	2,420,000	(2,460,000)
Purchases	25,112,000	22,843,000	25,483,000	23,118,000
Settlements	(6,682,000)	(6,858,000)	(9,814,000)	(10,398,000)
Ending balance	25,133,000	$ 17,943,000	25,133,000	$ 17,943,000
QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) | Measured On A Recurring Basis
Asset description
Institutional money market funds	0		0		0
FTRs	0		0		0
Total assets	0		0		0
Liability description
FTRs	0		0		0
Total liabilities	0		0		0
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | Measured On A Recurring Basis
Asset description
Institutional money market funds	141,290,000		141,290,000		144,302,000
FTRs	0		0		0
Total assets	141,290,000		141,290,000		144,302,000
Liability description
FTRs	0		0		0
Total liabilities	0		0		0
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | Measured On A Recurring Basis
Asset description
Institutional money market funds	0		0		0
FTRs	26,077,000		26,077,000		7,396,000
Total assets	26,077,000		26,077,000		7,396,000
Liability description
FTRs	944,000		944,000		352,000
Total liabilities	944,000		944,000		352,000
CLECO POWER
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value, concentration of risk, amount of money market funds in cash and cash equivalents	67,800,000		67,800,000		62,500,000
CLECO POWER | Restricted Cash and Cash Equivalents, Current
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	9,900,000		9,900,000		13,100,000
CLECO POWER | Restricted Cash and Cash Equivalents, Noncurrent
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	18,900,000		18,900,000		20,100,000
CLECO POWER | Measured On A Recurring Basis
Asset description
Institutional money market funds	96,568,000		96,568,000		95,681,000
FTRs	26,077,000		26,077,000		7,396,000
Total assets	122,645,000		122,645,000		103,077,000
Liability description
FTRs	944,000		944,000		352,000
Total liabilities	944,000		944,000		352,000
CLECO POWER | QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) | Measured On A Recurring Basis
Asset description
Institutional money market funds	0		0		0
FTRs	0		0		0
Total assets	0		0		0
Liability description
FTRs	0		0		0
Total liabilities	0		0		0
CLECO POWER | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | Measured On A Recurring Basis
Asset description
Institutional money market funds	96,568,000		96,568,000		95,681,000
FTRs	0		0		0
Total assets	96,568,000		96,568,000		95,681,000
Liability description
FTRs	0		0		0
Total liabilities	0		0		0
CLECO POWER | SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | Measured On A Recurring Basis
Asset description
Institutional money market funds	0		0		0
FTRs	26,077,000		26,077,000		7,396,000
Total assets	26,077,000		26,077,000		7,396,000
Liability description
FTRs	944,000		944,000		352,000
Total liabilities	$ 944,000		$ 944,000		$ 352,000