Fair Value Measurements Fair Value Disclosure, Additional Information (Details) € in Billions, ¥ in Billions	Sep. 30, 2016 USD ($) Swap	Sep. 30, 2016 EUR (€) Swap	Sep. 30, 2016 JPY (¥) Swap	Sep. 30, 2015 USD ($) Swap	Sep. 30, 2015 EUR (€) Swap	Sep. 30, 2015 JPY (¥) Swap	Jun. 30, 2014 USD ($) Swap	Sep. 30, 2013 USD ($) Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of fixed to floating interest rate swaps outstanding | Swap	8	8	8	12	12	12
Debt Instrument, Fair Value Disclosure	$ 9,300,000,000			$ 6,700,000,000
5.5 % Due in 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.50%	5.50%	5.50%	5.50%	5.50%	5.50%
2.6 % Due in 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.60%	2.60%	2.60%	2.60%	2.60%	2.60%
1.4% Due in 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.40%	1.40%	1.40%	1.40%	1.40%	1.40%
7.125 % Due in 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.125%	7.125%	7.125%	7.125%	7.125%	7.125%
Foreign Currency Denominated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount		€ 1	¥ 37		€ 0	¥ 0
Interest Rate Swap [Member] | 5.5 % Due in 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Amount of Hedged Item								$ 800,000,000
Debt Instrument, Interest Rate, Stated Percentage								5.50%
Number of fixed to floating interest rate swaps outstanding | Swap								4
Interest Rate Swap [Member] | 2.6 % Due in 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Amount of Hedged Item							$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage							2.60%
Number of fixed to floating interest rate swaps outstanding | Swap							4
Interest Rate Swap [Member] | 1.4% Due in 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Amount of Hedged Item							$ 300,000,000
Debt Instrument, Interest Rate, Stated Percentage							1.40%
Number of fixed to floating interest rate swaps outstanding | Swap							3
Interest Rate Swap [Member] | 7.125 % Due in 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Amount of Hedged Item							$ 150,000,000
Debt Instrument, Interest Rate, Stated Percentage							7.125%
Number of fixed to floating interest rate swaps outstanding | Swap							1
Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of fixed to floating interest rate swaps outstanding | Swap	0	0	0	4	4	4
Derivative, Notional Amount				$ 20,000,000,000
Unrealized Loss [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	$ 1,000,000
Unrealized Gains [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax				$ 0