Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018
Income Tax Contingency [Line Items]
Income tax (expense) benefit	$ 3		$ 45		$ 292	$ 12
Income (loss) before income tax (expense) benefit	$ (1,107)		$ 45		(797)	(207)
Provisional charges recorded		$ 174			174
Income tax related to non-cash write-down of assets and investments						121
Gross income tax paid					116	89
Income tax refunds					$ 6	$ 1
Tax Cuts and Jobs Act of 2017 [Member]
Income Tax Contingency [Line Items]
Deemed patriation tax charge		34		$ 34
Deferred deferred tax charge due to re-measurement of U.S. deferred tax assets		$ (140)		$ (140)
Scenario, Forecast [Member]
Income Tax Contingency [Line Items]
U.S. statutory federal tax rate							21.00%	28.00%