Debt (Debt Textuals) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2016	Feb. 08, 2016	Sep. 30, 2015
Debt Instruments [Abstract]
Prior Period Reclassification Adjustment		$ 152
Debt Instrument, Interest Rate, Effective Percentage			5.50%		5.70%
Corporate Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Increase (Decrease), Net	$ 178
Line of Credit Facility, Maximum Borrowing Capacity				$ 1,678
Future line of credit facility maximum borrowing capacity on June 27, 2018	$ 1,520
Increase in Letter of Credit Sublimit				250
Total Letter of Credit Sublimit				$ 1,000
Extension of Line of Credit Revolver	2 years