Pension and Other Postretirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2013 Pension and Postretirement Plans [Member]	Dec. 31, 2012 Pension and Postretirement Plans [Member]	Dec. 31, 2013 Pension and Postretirement Plans [Member]	Dec. 31, 2012 Pension and Postretirement Plans [Member]	Dec. 31, 2013 Pension and Postretirement Plans [Member] LMG Non-Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlements, curtailments and other	$ 1		$ 1
Company contributions made to various plans				17	14	28	26	8
Third party contributions made to pension plans		37
Reduction in retirement benefit obligation due to changes made in retiree medical plans			$ 41