Financing - Schedule of Line of Credit Facilities (Details)	Jun. 30, 2016 USD ($)
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	$ 6,500,000,000
Remaining Borrowing Capacity	6,387,000,000
Southern Power [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	600,000,000
Remaining Borrowing Capacity	560,000,000
Construction Loans [Member] | Southern Power [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	235,000,000
Construction Loans [Member] | Southern Power [Member] | RE Tranquility Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	86,000,000
Construction Loans [Member] | Southern Power [Member] | RE Roserock Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	63,000,000
Construction Loans [Member] | Southern Power [Member] | RE Garland Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	86,000,000
Bridge Loan [Member] | Southern Power [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	660,000,000
Bridge Loan [Member] | Southern Power [Member] | RE Tranquility Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	172,000,000
Bridge Loan [Member] | Southern Power [Member] | RE Roserock Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	180,000,000
Bridge Loan [Member] | Southern Power [Member] | RE Garland Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	308,000,000
Construction Loan And Bridge Loan [Member] | Southern Power [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	895,000,000
Remaining Borrowing Capacity	126,000,000
Construction Loan And Bridge Loan [Member] | Southern Power [Member] | RE Tranquility Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	258,000,000
Remaining Borrowing Capacity	19,000,000
Construction Loan And Bridge Loan [Member] | Southern Power [Member] | RE Roserock Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	243,000,000
Remaining Borrowing Capacity	34,000,000
Construction Loan And Bridge Loan [Member] | Southern Power [Member] | RE Garland Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	394,000,000
Remaining Borrowing Capacity	73,000,000
Letter of Credit [Member] | Southern Power [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	149,000,000
Remaining Borrowing Capacity	65,000,000
Letter of Credit [Member] | Southern Power [Member] | RE Tranquility Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	77,000,000
Remaining Borrowing Capacity	26,000,000
Letter of Credit [Member] | Southern Power [Member] | RE Roserock Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	23,000,000
Remaining Borrowing Capacity	16,000,000
Letter of Credit [Member] | Southern Power [Member] | RE Garland Holdings, LLC [Member]
Line of Credit Facility [Line Items]
Maximum Borrowing Capacity	49,000,000
Remaining Borrowing Capacity	$ 23,000,000