Net Postretirement Benefit Cost Recognized (Detail) (Other Postretirement Benefit Plans, Defined Benefit, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 181	$ 136	$ 362	$ 275
Interest cost	881	980	1,762	1,962
Net amortization and deferral and other	129	(113)	258	(228)
Net benefit cost	$ 1,191	$ 1,003	$ 2,382	$ 2,009