Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2017
Pension plans
Components of net periodic (benefit) expense
Service cost	$ 17	$ 17
Interest cost	101	107
Expected return on plan assets	(166)	(184)
Recognition of prior service (credit) cost	(2)	(2)
Recognition of actuarial loss	51	42
Net periodic benefit (income) expense	1	(20)
Post-retirement benefit plans
Components of net periodic (benefit) expense
Service cost	4	5
Interest cost	25	28
Expected return on plan assets	0	(2)
Recognition of prior service (credit) cost	5	5
Net periodic benefit (income) expense	$ 34	$ 36
Scenario, Forecast | Pension plans
Employee Benefits
Voluntary contributions to plan by employer			$ 100