Subsequent Events (Details) (Subsequent Event [Member], USD $) In Millions, unless otherwise specified	Oct. 31, 2012
Subsequent Event [Member]
Subsequent Events [Line Items]
Interest In Geismar To Be Contributed	83.30%
Consideration To Be Received	$ 2,364

Our percentage ownership of Geismar facility to be sold to WPZ

No definition available.

Name:	wmb_InterestInGeismarToBeContributed
Namespace Prefix:	wmb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant