Retirement Benefit Obligations - Schedule of Allocation of Plan Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,506	$ 1,535	$ 1,286
Money Market Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	6
Domestic Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	88	87
International Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	312	332
Domestic Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	162	149
International Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	585	543
Balanced Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	337	377
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18	41
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	110	134
Level 1 [Member] | International Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	104	105
Level 1 [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6	29
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,384	1,389
Level 2 [Member] | Money Market Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	6
Level 2 [Member] | Domestic Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	88	87
Level 2 [Member] | International Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	208	227
Level 2 [Member] | Domestic Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	162	149
Level 2 [Member] | International Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	585	543
Level 2 [Member] | Balanced Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	337	377
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12	12	$ 11
Level 3 [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 12	$ 12