Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Income taxes, net of refunds	$ (3,019)	$ 12,535	$ 21,173
Interest, net of amounts capitalized	216,951	218,664	208,479
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Accrued capital expenditures	113,502	141,297	132,620
Dividends declared but not paid	93,531	87,982	82,675
Sale of 4CA 7% interest in Four Corners	$ 0	0	68,907
4CA | El Paso's Interest in Four Corners
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Ownership interest acquired (as a percent)	7.00%
ARIZONA PUBLIC SERVICE COMPANY
Cash and Cash Equivalents [Line Items]
Income taxes, net of refunds	$ 41,176	(15,042)	77,942
Interest, net of amounts capitalized	206,328	204,261	196,419
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Accrued capital expenditures	113,502	141,297	132,620
Dividends declared but not paid	$ 93,500	$ 88,000	$ 82,700