Employee benefit plans

3 Months Ended

Mar. 31, 2018

Retirement Benefits [Abstract]

Pension and other postretirement benefit plans

Employee benefit plans

Pension and other postretirement plans

The Company has qualified defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Components of net periodic benefit cost (credit) for the Company's pension and other postretirement benefit plans were as follows:

	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2018			2017			2018			2017
	(In thousands)
Components of net periodic benefit cost (credit):
Service cost	$	—		$	—		$	407		$	447
Interest cost	3,807			4,014			778			808
Expected return on assets	(4,998		)	(5,029		)	(1,167		)	(1,145		)
Amortization of prior service credit	—			—			(349		)	(343		)
Amortization of net actuarial loss	1,782			1,793			238			336
Net periodic benefit cost (credit), including amount capitalized	591			778			(93		)	103
Less amount capitalized	—			107			40			(39		)
Net periodic benefit cost (credit)	$	591		$	671		$	(133	)	$	142

The components of net periodic benefit cost (credit), other than the service cost component, are included in other income on the Company's Consolidated Statements of Income.

Nonqualified defined benefit plans

In addition to the qualified defined pension benefit plans reflected in the table, the Company also has unfunded, nonqualified defined benefit plans for executive officers and certain key management employees that generally provide for defined benefit payments at age 65 following the employee's retirement or, upon death, to their beneficiaries for a 15-year period. In February 2016, the Company froze the unfunded, nonqualified defined benefit plans to new participants and eliminated benefit increases. Vesting for participants not fully vested was retained. The Company's net periodic benefit cost for these plans was $1.1 million and $1.2 million for the three months ended March 31, 2018 and 2017, respectively. In accordance with ASU 2017-07, the components of net periodic benefit cost, which does not contain any service costs, have been classified as other income on the Company's Consolidated Statements of Income.