Debt (Tables)
 6 Months Ended
Mar. 31, 2016
Debt Disclosure [Abstract]  
Schedule of Short-term Debt
Short-term Debt
(in millions, except weighted average amounts)
March 31,
2016
 
September 30,
2015
Short-term commercial paper borrowings outstanding (1)
$
820

 
$
448

Current portion of long-term debt
300

 
—

Short-term debt
$
1,120

 
$
448

Weighted average interest rate of commercial paper borrowings
0.76
%
 
0.52
%
Weighted average maturity period of commercial paper borrowings (days)
17

 
25

(1) The maximum amount of short-term commercial paper borrowings outstanding during the six months ended March 31, 2016 was $929 million
Long-Term Debt Reconciliation to Carrying Amount
The principal amount of long-term debt, net of discount, is summarized as follows:
(in millions, except interest rate figures)
Interest Rate
 
March 31,
2016
 
September 30,
2015
Fixed-rate notes due:
 
 
 
 
 
December 2043
4.80%
 
$
398

 
$
398

December 2023
3.70%
 
399

 
399

November 2021
3.10%
 
250

 
250

July 2019
5.25%
 
299

 
299

Variable-rate note due:
 
 
 
 
 
December 2016
3 month LIBOR + 0.35% (1)
 
300

 
300

Fair value swap adjustment (see Notes 13 and 14)
 
 
37

 
34

Total
 
 
1,683

 
1,680

Less current portion of long-term debt
 
 
300

 
—

Long-term Debt, Net
 
 
$
1,383

 
$
1,680

(1) The three-month LIBOR rate at March 31, 2016 was approximately 0.63 percent