Pension and Other Postretirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended	3 Months Ended	9 Months Ended
	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Settlements, curtailments and other	$ 0		$ 1
Third party contributions made to pension plans		37
Pension and Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions made to various plans	13		41	4	13
Pension and Postretirement Plans [Member] | LMG Non-Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions made to various plans			8
Retiree Medical Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Reduction in Retirement benefit obligation due to changes made in defined benefit pension and retiree medical plans		$ 41