Pension and Non-pension Post-retirement Benefits

The components of our net pension expense, including the SERP (supplemental employee retirement plan), are as follows:



Three months ended March 31,	U.S. Plans						Non-U.S. Plans						Total
(dollars in thousands)	2019			2018			2019			2018			2019			2018
Service cost	$	783		$	979		$	259		$	292		$	1,042		$	1,271
Interest cost	3,382			3,165			769			763			4,151			3,928
Expected return on plan assets	(5,193		)	(5,660		)	—			—			(5,193		)	(5,660		)
Amortization of unrecognized:
Prior service (credit)	—			—			(50		)	(51		)	(50		)	(51		)
Actuarial loss	1,087			1,637			103			159			1,190			1,796
Pension expense	$	59		$	121		$	1,081		$	1,163		$	1,140		$	1,284

We have contributed $1.3 million of cash to our pension plans for the three months ended March 31, 2019. Pension contributions for the remainder of 2019 are estimated to be $2.1 million.

The provision for our non-pension, post-retirement, benefit expense consists of the following:



Three months ended March 31,	U.S. Plans						Non-U.S. Plans						Total
(dollars in thousands)	2019			2018			2019			2018			2019			2018
Service cost	$	110		$	151		$	—		$	—		$	110		$	151
Interest cost	469			456			9			10			478			466
Amortization of unrecognized:
Prior service (credit)	(70		)	(71		)	—			—			(70		)	(71		)
Actuarial (gain)	(82		)	(52		)	(18		)	(16		)	(100		)	(68		)
Non-pension post-retirement benefit expense	$	427		$	484		$	(9	)	$	(6	)	$	418		$	478

Our 2019 estimate of non-pension cash payments is $4.0 million, of which we have paid $1.8 million for the three months ended March 31, 2019.