Employee Benefit Plans

9 Months Ended

Sep. 30, 2020

Retirement Benefits [Abstract]

Pension and Other Postretirement Benefits Disclosure [Text Block]

Employee Benefit Plans

We sponsor and/or contribute to pension and postretirement health care and life insurance benefit plans for eligible employees. Net periodic benefit cost (credit) for our pension and other postretirement plans consists of the following (in thousands):

	Pension Benefits				Other Postretirement Benefits
	Three Months Ended September 30,				Three Months Ended September 30,
	2020		2019		2020		2019
Components of Net Periodic Benefit Cost (Credit)
Service cost	$	2,779	$	2,409	$	93	$	82
Interest cost	5,710		6,622		123		152
Expected return on plan assets	(6,541)		(6,360)		(246)		(217)
Amortization of prior service cost (credit)	—		1,636		(471)		(471)
Recognized actuarial loss (gain)	1,257		—		(15)		(24)
Plan settlements	—		715		—		—
Net periodic benefit cost (credit)	$	3,205	$	5,022	$	(516)	$	(478)

	Pension Benefits				Other Postretirement Benefits
	Nine Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Components of Net Periodic Benefit Cost (Credit)
Service cost	$	8,337	$	7,228	$	278	$	248
Interest cost	17,130		19,866		369		457
Expected return on plan assets	(19,622)		(19,082)		(738)		(652)
Amortization of prior service cost (credit)	—		4,908		(1,412)		(1,412)
Recognized actuarial loss (gain)	3,771		—		(45)		(72)
Plan settlements	—		715		—		—
Net periodic benefit cost (credit)	$	9,616	$	13,635	$	(1,548)	$	(1,431)

We contributed $11.4 million to our pension plans during the nine months ended September 30, 2020. As discussed in Note 2 Regulatory Matters, we have not yet determined whether we will contribute incremental amounts to the Montana pension plan during the fourth quarter of 2020.