Pension Benefits | Other Postemployment Benefits | ||||||||||||||||||||||
(in thousands) | 2013 | 2012 | 2011 | 2013 | 2012 | 2011 | |||||||||||||||||
Service cost | $ | 14,863 | $ | 12,178 | $ | 10,950 | $ | 234 | $ | 195 | $ | 61 | |||||||||||
Interest cost | 9,901 | 10,600 | 9,633 | 464 | 490 | 553 | |||||||||||||||||
Expected return on assets | (4,998 | ) | (4,727 | ) | (5,184 | ) | — | — | — | ||||||||||||||
Amortization of prior service cost (credit) | (133 | ) | (138 | ) | 80 | 2 | — | — | |||||||||||||||
Amortization of net actuarial loss | 5,150 | 1,995 | 1,584 | 303 | 264 | 189 | |||||||||||||||||
Curtailment and settlement gains | (1,600 | ) | (303 | ) | 4 | — | — | — | |||||||||||||||
Net periodic benefit cost | $ | 23,183 | $ | 19,605 | $ | 17,067 | $ | 1,003 | $ | 949 | $ | 803 | |||||||||||