Net Postretirement Benefit Cost Recognized (Detail) (Other Postretirement Benefit Plans, Defined Benefit, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 183	$ 233	$ 545	$ 508
Interest cost	838	724	2,600	2,686
Net amortization and deferral and other	92	621	350	393
Net benefit cost	$ 1,113	$ 1,578	$ 3,495	$ 3,587