Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Regulatory liabilities	$ (355,725)	$ (323,032)
Regulatory Liabilities	358,957	327,153
Salary and Wage, Excluding Cost of Good and Service Sold [Abstract]
Stock-based compensation expense	1,300	1,500	$ 1,800
Other Postretirement Benefit Costs
Defined Benefit Plan Disclosure [Line Items]
Regulatory liabilities	(39,400)	(37,700)
Williams Companies Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension cost	1,900	2,200	3,900
Defined contribution plan matching contributions expense	2,300	1,800	1,900
Williams Companies Inc [Member] | Retiree health care and life insurance benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Regulatory liabilities	(1,700)	$ (1,500)	(2,100)
Williams Companies Inc [Member] | Pension Plan [Member] | Directly charged [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension cost charges to us by Williams	$ 700		$ 1,300