Retirement benefits (Notes)

9 Months Ended

Mar. 31, 2017

Compensation and Retirement Disclosure [Abstract]

Retirement benefits

Retirement benefits

Net pension benefit cost recognized included the following components:

	Three Months Ended						Nine Months Ended
	March 31,						March 31,
	2017			2016			2017			2016
Service cost	$	23,632		$	23,680		$	70,971		$	71,199
Interest cost	31,734			45,138			93,202			136,872
Special termination cost	—			—			—			7,088
Expected return on plan assets	(59,480		)	(55,418		)	(177,277		)	(166,633		)
Amortization of prior service cost	1,702			1,868			5,101			5,606
Amortization of net actuarial loss	52,805			42,573			158,557			127,841
Amortization of initial net obligation	4			4			14			12
Net pension benefit cost	$	50,397		$	57,845		$	150,568		$	181,985

During the three months ended March 31, 2017 and 2016, the Company recognized $1,034 and $1,001, respectively, in expense related to other postretirement benefits. During the nine months ended March 31, 2017 and 2016, the Company recognized $3,266 and $7,696, respectively, in expense related to other postretirement benefits.

12. Retirement benefits, cont'd

During the nine months ended March 31, 2016, the Company provided enhanced retirement benefits in connection with a plant closure, which resulted in an increase in net pension benefit cost of $7,088 and an increase in expense related to other postretirement benefits of $4,521.

Beginning in fiscal 2017, the Company changed the method used to estimate the service and interest cost components of net periodic pension and other postretirement benefit costs. The new method uses the spot yield curve approach to estimate the service and interest costs by applying the specific spot rates along the yield curve used to determine the benefit obligations to relevant cash outflows. Previously, these costs were determined using a single-weighted average discount rate. The change does not affect the measurement of the Company's benefit obligations. The new method provides a more precise measure of service and interest costs by improving the correlation between projected benefit cash flows and the discrete spot yield curve rates and is accounted for as a change in estimate prospectively beginning the first quarter of fiscal 2017. As a result of the method change, net pension benefit cost for the current-year quarter and first nine months of fiscal 2017 is lower than the prior-year quarter and first nine months of fiscal 2016 by approximately $8 million and $25 million, respectively,