Asset Securitizations And Off-Balance Sheet Arrangement	12 Months Ended
Dec. 31, 2011
Asset Securitizations And Off-Balance Sheet Arrangement [Abstract]
Asset Securitizations And Off-Balance Sheet Arrangement	7. ASSET SECURITIZATIONS AND OFF-BALANCE SHEET ARRANGEMENT In June 2009, Zions Bank fully consolidated Lockhart, which previously functioned as an off-balance sheet qualifying special-purpose entity ("QSPE") securities conduit. As of September 30, 2009, Lockhart was legally terminated. Prior to this consolidation, Zions Bank purchased $678 million of securities at book value from Lockhart in 2009. Valuation losses resulting from these purchases were $187.9 million. The purchases of securities from Lockhart were made due to investment downgrades as required under a liquidity agreement between Zions Bank and Lockhart, and due to the inability of Lockhart to issue a sufficient amount of commercial paper. Effective January 1, 2010, we adopted ASU No. 2009-16, Accounting for Transfers of Financial Assets, an amendment of FASB Statement No. 140. This new accounting guidance under ASC 860 modifies the accounting for transfers of financial assets and removes the concept of a QSPE. Because we dissolved Lockhart and our remaining activities related to transfers of financial assets have not been material, adoption of this new guidance was not significant to the Company's financial statements.

7. ASSET SECURITIZATIONS AND OFF-BALANCE SHEET ARRANGEMENT

In June 2009, Zions Bank fully consolidated Lockhart, which previously functioned as an off-balance sheet qualifying special-purpose entity ("QSPE") securities conduit. As of September 30, 2009, Lockhart was legally terminated. Prior to this consolidation, Zions Bank purchased $678 million of securities at book value from Lockhart in 2009. Valuation losses resulting from these purchases were $187.9 million. The purchases of securities from Lockhart were made due to investment downgrades as required under a liquidity agreement between Zions Bank and Lockhart, and due to the inability of Lockhart to issue a sufficient amount of commercial paper.

Effective January 1, 2010, we adopted ASU No. 2009-16, Accounting for Transfers of Financial Assets, an amendment of FASB Statement No. 140. This new accounting guidance under ASC 860 modifies the accounting for transfers of financial assets and removes the concept of a QSPE. Because we dissolved Lockhart and our remaining activities related to transfers of financial assets have not been material, adoption of this new guidance was not significant to the Company's financial statements.