Description of Business and Significant Accounting Policies - Basis of Presentation and Consolidation (Details) - USD ($)	Sep. 30, 2016	Sep. 30, 2015
Accounting Policies [Abstract]
Cash and Cash Equivalents - Deposits and Receivables	$ 900,000,000	$ 900,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Outstanding	0	0
US Government Securities and Other Securities - Deposits and Receivables	$ 471,738,813	$ 502,483,279