Pensions and Other Postretirement Benefits - Components of Pension and Retiree Health Care Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Pension Benefit Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,627	$ 1,381	$ 4,881	$ 4,143
Interest cost	2,060	2,123	6,180	6,369
Expected return on plan assets	(2,272)	(2,166)	(6,816)	(6,498)
Amortization of prior service cost	65	65	195	195
Recognized actuarial losses	681	290	2,043	870
Amortization of transition obligation	10	10	30	30
Other income	(59)	0	(177)	0
Benefit cost	2,112	1,703	6,336	5,109
Retiree Health Care Benefit Cost [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	39	274	397	822
Interest cost	140	586	822	1,758
Amortization of prior service cost	(2,572)	(516)	(3,604)	(1,548)
Recognized actuarial losses	(65)	82	(423)	246
Benefit cost	$ (2,458)	$ 426	$ (2,808)	$ 1,278