From RIGs latest 10k

"There have also been numerous lawsuits filed related to the incident, and we expect additional lawsuits to be filed. We expect to incur significant legal fees and costs in responding to these matters. As a result of the incident, our business will be negatively impacted by the loss of revenue from the rig. We do not carry insurance for loss of revenue. The rig is insured for total loss coverage of $560 million and wreck removal, subject to certain policy limits, to the extent removal can be carried out and is required. Under our drilling contract for Deepwater Horizon, the operator has agreed, among other things, to assume full responsibility for and defend, release and indemnify us from any loss, expense, claim, fine, penalty or liability for pollution or contamination, including control and removal thereof, arising out of or connected with operations under the contract (other than for pollution or contamination originating on or above the surface of the water from fuels, lubricants, motor oils and other substances, as to which we similarly agreed to assume responsibility and protect, release and indemnify the operator."

In addition there is a oil disaster trust fund (dismantled by Clinton and reestablished by Bush) that can pay up to $2 billion of the cleanup.