Pension Plans | OPEB Plans | ||||||||||||
(Millions) | 2013 | 2012 | 2013 | 2012 | |||||||||
Benefit obligation, beginning of year | $ | 6,665.8 | $ | 6,130.3 | $ | 292.4 | $ | 312.7 | |||||
Service cost | — | — | .1 | .1 | |||||||||
Interest cost | 271.5 | 298.4 | 11.1 | 14.4 | |||||||||
Actuarial (gain) loss | (653.7 | ) | 550.2 | (22.5 | ) | (11.4 | ) | ||||||
Benefits paid | (318.3 | ) | (313.1 | ) | (20.2 | ) | (23.4 | ) | |||||
Benefit obligation, end of year | $ | 5,965.3 | $ | 6,665.8 | $ | 260.9 | $ | 292.4 | |||||