Commitments and Contingent Liabilities - (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended	109 Months Ended
	Jan. 31, 2015	May 31, 2017	May 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
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