Leases Lessor - Narrative (Details)	3 Months Ended
	Mar. 31, 2019
Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	1 year
Options to extend the term, Lessor, Operating Lease	1 years
Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	84 years
Options to extend the term, Lessor, Operating Lease	79 years
Exelon Generation Co L L C [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	1 year
Options to extend the term, Lessor, Operating Lease	1 years
Exelon Generation Co L L C [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	33 years
Options to extend the term, Lessor, Operating Lease	5 years
Commonwealth Edison Co [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	1 year
Options to extend the term, Lessor, Operating Lease	5 years
Commonwealth Edison Co [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	18 years
Options to extend the term, Lessor, Operating Lease	79 years
PECO Energy Co [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	1 year
Options to extend the term, Lessor, Operating Lease	5 years
PECO Energy Co [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	84 years
Options to extend the term, Lessor, Operating Lease	50 years
Baltimore Gas and Electric Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	24 years
Baltimore Gas and Electric Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	24 years
Pepco Holdings LLC [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	1 year
Options to extend the term, Lessor, Operating Lease	5 years
Pepco Holdings LLC [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	14 years
Options to extend the term, Lessor, Operating Lease	5 years
Potomac Electric Power Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	2 years
Potomac Electric Power Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	7 years
Delmarva Power and Light Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	13 years
Delmarva Power and Light Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	14 years
Atlantic City Electric Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	1 year
Atlantic City Electric Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms, Lessor, Operating Lease	3 years
Contracted Generation [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Contracted Generation [Member] | Exelon Generation Co L L C [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Exelon Generation Co L L C [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Commonwealth Edison Co [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | PECO Energy Co [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Baltimore Gas and Electric Company [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Pepco Holdings LLC [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Potomac Electric Power Company [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Delmarva Power and Light Company [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member] | Atlantic City Electric Company [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●