U.S. and Europe Retrospective Responsibility Plans (Details) € in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 EUR (€)	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Escrow account	$ 1,030,000,000		$ 1,030,000,000	$ 1,027,000,000
VE territory covered loss, maximum amount of loss to allow adjustment of conversion rate during six-month period | €		€ 20
Recovery through conversion rate adjustment			(191,000,000)
Preferred stock, conversion ratio				13.952
U.K.& I preferred stock
Restricted Cash and Cash Equivalents Items [Line Items]
Recovery through conversion rate adjustment	$ 71,000,000		$ 190,280,000.00
Preferred stock, conversion ratio	13.0770		13.0770
Europe preferred stock
Restricted Cash and Cash Equivalents Items [Line Items]
Recovery through conversion rate adjustment			$ 1,000,000
Preferred stock, conversion ratio	13.9480		13.9480