Fair Value Fair Value (Details 4) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Fair Value, Inputs, Level 1 [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable, excluding capital leases	$ 0
Dividends Payable Fair Value Disclosure	100
Short-term borrowing	0
Long-term debt	300
Fair Value, Inputs, Level 2 [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable, excluding capital leases	0
Dividends Payable Fair Value Disclosure	0
Short-term borrowing	313
Long-term debt	7,700
Fair Value, Inputs, Level 3 [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable, excluding capital leases	46
Dividends Payable Fair Value Disclosure	0
Short-term borrowing	0
Long-term debt	600
Total [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable, excluding capital leases	46
Dividends Payable Fair Value Disclosure	100
Short-term borrowing	313
Long-term debt	$ 8,600