Commitments and Contingent Liabilities - (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended	9 Months Ended	109 Months Ended
	Apr. 12, 2017	Jan. 31, 2015	Aug. 31, 2017	Jan. 31, 2015	Dec. 31, 2005
Loss Contingencies [Line Items]
Amount paid on contract				$ 20
District of Maryland
Loss Contingencies [Line Items]
Accrual for litigation			$ 140
District of Maryland | Judicial Ruling
Loss Contingencies [Line Items]
Purchase price in litigation	$ 114	$ 114
Litigation interest rate		12.00%		12.00%
Interest and other closing costs	$ 124
Original Contract
Loss Contingencies [Line Items]
Purchase price					$ 200
Renegotiated Contract
Loss Contingencies [Line Items]
Purchase price		$ 134		$ 134