Transactions with Affiliates (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Amounts paid to the Williams Entities
Percentage of owner of company in affiliated partnership	23.30%
Percentage of ownership of afffiliates of the company in the partnership	31.90%
Affiliated Entity [Member]
Amounts received from the Williams Entities
Services	$ 671		$ 566		$ 513
Insurance premiums and benefits	920		821		859
Reimbursed expenses	566		371		319
Amount received from Williams Entities	2,157		1,758		1,691
Amounts paid to the Williams Entities
Rent	1,478	[1]	843	[1]	811	[1]
Business entertainment	116	[2]	116	[2]	116	[2]
Reimbursed expenses	267		289		146
Amounts paid to the Williams Entities	$ 1,861		$ 1,248		$ 1,073

[1] Rent amounts were paid to a Partnership within the Williams Entities. The Company owns 31.9% of the Partnership and affiliates of the Company own 23.3%.

[2] Consists of hunting and fishing rights pertaining to land owned by affiliates of Mr. Williams.