W&T Offshore, Inc. Quarterly report pursuant to Section 13 or 15(d)

Contingencies - (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended			3 Months Ended	12 Months Ended
	Sep. 30, 2012 Cameron Parish Louisiana Claim [Member]	Sep. 30, 2012 Contingent Liability Recorded [Member]	Sep. 30, 2011 Contingent Liability Recorded [Member]	Sep. 30, 2012 Contingent Liability Recorded [Member]	Sep. 30, 2011 Contingent Liability Recorded [Member]	Dec. 31, 2011 Contingent Liability Recorded [Member]	Sep. 30, 2010 Royalties [Member]	Dec. 31, 2009 Royalties [Member]
Claims paid	$ 9.0
Accrued claims	1.8
Expenses related to accrued and settled claims		0.4	0.4	8.8	0.2
Liability loss contingency		1.8		1.8		2.0
Allowable reductions of cash payments								5.3
Notified disallowed amount in reductions taken by ONRR							$ 4.7