SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT General (Details)	Dec. 31, 2015
Condensed Financial Statements, Captions
FERC approved capital structure, equity percentage	60.00%
FERC approved capital structure, debt percentage	40.00%
Regulated Operating Subsidiaries
Condensed Financial Statements, Captions
FERC approved capital structure, equity percentage	60.00%
FERC approved capital structure, debt percentage	40.00%