Retirement Plans | Other Benefit Plans | ||||||||||||||||||
(Dollars in Millions) | 2013 | 2012 | 2011 | 2013 | 2012 | 2011 | |||||||||||||
Service cost | $ | 906 | 722 | 638 | 196 | 175 | 149 | ||||||||||||
Interest cost | 908 | 878 | 853 | 151 | 165 | 188 | |||||||||||||
Expected return on plan assets | (1,447 | ) | (1,236 | ) | (1,108 | ) | (6 | ) | (4 | ) | (1 | ) | |||||||
Amortization of prior service cost (credit) | 6 | 6 | 9 | (2 | ) | (3 | ) | (3 | ) | ||||||||||
Amortization of net transition obligation | 1 | 1 | 1 | — | — | — | |||||||||||||
Recognized actuarial losses | 681 | 494 | 388 | 111 | 76 | 45 | |||||||||||||
Curtailments and settlements | — | — | — | 2 | — | — | |||||||||||||
Net periodic benefit cost | $ | 1,055 | 865 | 781 | 452 | 409 | 378 |