Gain on realization of marketable securities	12 Months Ended
Dec. 31, 2012
Gain on realization of marketable securities [Abstract]
Gain on realization of marketable securities	Note 34 – Gain on realization of marketable securities On May 17, 2012, SapuraCrest (BURSA: SCRES) and Kencana (BURSA: KEPB) jointly announced that they have entered into a merger agreement forming a new company, SapuraKencana Petroleum BHD (SapuraKencana). Consequently Seadrill received 589 million shares in the new company and a cash payment of $65 million. This merger resulted in a dilution of our equity share from 23.59% to 11.79% and a recognized gain on decline in ownership of $169 million represented on a separate line item in our statement of operations. On May 30, 2012, Seadrill announced the sale of 300 million shares in SapuraKencana resulting in a gain of $84 million reported as gain on realization of marketable securities in our statement of operation. Seadrill's holding of shares in SapuraKencana following this transaction represents 6.4% ownership of the outstanding shares. The net proceed from the sale of these shares was $198 million. On February 7, 2011, Ensco plc ("Ensco") (NYSE: ESV) and Pride International, Inc. ("Pride") (NYSE: PDE) jointly announced that they have entered into a definitive merger agreement under which Ensco will combine with Pride in a cash and stock transaction. On May 31, 2011, Ensco announced the completion of its acquisition of Pride International, after both companies received shareholder approvals. Under the terms of the merger agreement, Pride stockholders received 0.4778 newly-issued shares of Ensco plus $15.60 in cash for each share of Pride common stock. The merger represents a realization of our previously held Pride positions. The accumulated other-comprehensive income effect related to our holding in Pride amounted to $416 million as of May 31, 2011. This amount has been released into the profit and loss statement upon our acceptance of the Ensco offer, and the gain is presented on a separate line item in our financial statements. The cash effect of this transaction was $141 million in 2011.

Note 34 – Gain on realization of marketable securities

On May 17, 2012, SapuraCrest (BURSA: SCRES) and Kencana (BURSA: KEPB) jointly announced that they have entered into a merger agreement forming a new company, SapuraKencana Petroleum BHD (SapuraKencana). Consequently Seadrill received 589 million shares in the new company and a cash payment of $65 million.

This merger resulted in a dilution of our equity share from 23.59% to 11.79% and a recognized gain on decline in ownership of $169 million represented on a separate line item in our statement of operations.

On May 30, 2012, Seadrill announced the sale of 300 million shares in SapuraKencana resulting in a gain of $84 million reported as gain on realization of marketable securities in our statement of operation. Seadrill's holding of shares in SapuraKencana following this transaction represents 6.4% ownership of the outstanding shares. The net proceed from the sale of these shares was $198 million.

On February 7, 2011, Ensco plc ("Ensco") (NYSE: ESV) and Pride International, Inc. ("Pride") (NYSE: PDE) jointly announced that they have entered into a definitive merger agreement under which Ensco will combine with Pride in a cash and stock transaction. On May 31, 2011, Ensco announced the completion of its acquisition of Pride International, after both companies received shareholder approvals. Under the terms of the merger agreement, Pride stockholders received 0.4778 newly-issued shares of Ensco plus $15.60 in cash for each share of Pride common stock.

The merger represents a realization of our previously held Pride positions. The accumulated other-comprehensive income effect related to our holding in Pride amounted to $416 million as of May 31, 2011. This amount has been released into the profit and loss statement upon our acceptance of the Ensco offer, and the gain is presented on a separate line item in our financial statements. The cash effect of this transaction was $141 million in 2011.