Financing Receivables (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017
Schedule of Financial Receivables [Line Items]
Lease Receivable adjustment		$ 15	$ 55
Residual Value Adjustment		$ 7
Lease investment with non-investment grade counterparties, gross	$ 335
Lease investment with non-investment grade counterparties, net of deferred taxes	$ (88)
Powerton Station [Member]
Schedule of Financial Receivables [Line Items]
Counterparties’ S&P Credit Ratings	BB-