| The increase (decrease) in the present value of a defined benefit obligation resulting from past service cost. Past service cost is the change in the present value of the defined benefit obligation for employee service in prior periods, resulting in the current period from the introduction of, or changes to, post-employment benefits or other long-term employee benefits. [Refer: Defined benefit obligation, at present value] | en | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |