Debt Leases and Banking Arrangements (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Line of Credit Facility [Abstract]
Letters of Credit Outstanding, Amount	$ 21
Line of Credit Facility, Amount Outstanding	0
$ 900 million unsecured credit facility
Line of Credit Facility [Abstract]
Letters of Credit Outstanding, Amount	0
Line of Credit Facility, Amount Outstanding	0
$ 2 billion WPZ unsecured credit facility
Line of Credit Facility [Abstract]
Letters of Credit Outstanding, Amount	0
Line of Credit Facility, Amount Outstanding	0
Bilateral bank agreements for letters of credit
Line of Credit Facility [Abstract]
Letters of Credit Outstanding, Amount	$ 21