Organization	6 Months Ended
Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization PacWest Bancorp is a bank holding company registered under the Bank Holding Company Act of 1956, as amended. Our principal business is to serve as the holding company for our wholly-owned banking subsidiary, Pacific Western Bank. References to "Pacific Western" or the "Bank" refer to Pacific Western Bank together with its wholly-owned subsidiaries. References to “we,” "us," “our,” or the “Company,” refer to PacWest Bancorp together with its subsidiaries on a consolidated basis. When we refer to “PacWest” or to the holding company, we are referring to PacWest Bancorp, the parent company, on a stand‑alone basis. As of June 30, 2016, the Company had total assets of $21.1 billion, gross loans and leases of $14.7 billion, total deposits of $15.1 billion and total stockholders' equity of $4.5 billion. We are focused on relationship-based business banking to small, middle-market and venture-backed businesses nationwide. The Bank offers a broad range of loan and lease and deposit products and services through 79 full-service branches located throughout the State of California, one branch located in Durham, North Carolina, and several loan production offices located in cities across the country. The Bank provides commercial banking services, including real estate, construction, and commercial loans and leases, and comprehensive deposit and treasury management services to small and middle-market businesses. Pacific Western offers additional products and services through its CapitalSource and Square 1 Bank divisions. CapitalSource provides cash flow, asset-based, equipment and real estate loans and treasury management services to established middle-market businesses on a national basis. Square 1 Bank offers a comprehensive suite of financial services focused on entrepreneurial businesses and their venture capital and private equity investors, with offices located in key innovation hubs across the United States. In addition, we provide investment advisory and asset management services to select clients through Square 1 Asset Management, Inc., a wholly-owned subsidiary of the Bank and a SEC-registered investment adviser. When we refer to "CapitalSource Inc." we are referring to the company acquired on April 7, 2014 and when we refer to the "CapitalSource Division" we are referring to a division of Pacific Western. We generate our revenue primarily from interest received on loans and leases and, to a lesser extent, from interest received on investment securities, and fees received in connection with deposit services, extending credit and other services offered, including foreign exchange services. Our major operating expenses are compensation, occupancy, general operating expenses, and the interest paid by the Bank on deposits and borrowings. We have completed 28 acquisitions from May 1, 2000 through June 30, 2016, including the acquisition of Square 1 Financial, Inc. on October 6, 2015. Our acquisitions have been accounted for using the acquisition method of accounting and, accordingly, the operating results of the acquired entities have been included in the consolidated financial statements from their respective acquisition dates. See Note 2. Acquisitions, for more information about the Square 1 acquisition. On March 31, 2016, we sold our Pacific Western Equipment Finance ("PWEF") leasing unit in Midvale, Utah, including approximately $139 million of outstanding lease balances. Significant Accounting Policies Except as discussed below, our accounting policies are described in Note 1, Nature of Operations and Summary of Significant Accounting Policies, of our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2015 as filed with the Securities and Exchange Commission ("Form 10-K"). Basis of Presentation Our interim consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Article 10 of Regulation S-X of the Securities Exchange Act of 1934. Accordingly, certain disclosures accompanying annual consolidated financial statements are omitted. In the opinion of management, all significant intercompany accounts and transactions have been eliminated and adjustments, consisting solely of normal recurring accruals and considered necessary for the fair presentation of financial statements for the interim periods, have been included. The current period's results of operations are not necessarily indicative of the results that ultimately may be achieved for the year. The interim consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Form 10-K. Use of Estimates We have made a number of estimates and assumptions related to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period to prepare these condensed consolidated financial statements in conformity with U.S. GAAP. Material estimates subject to change in the near term include, among other items, the allowance for credit losses, the carrying value and useful lives of intangible assets, the realization of deferred tax assets, and the fair value estimates of assets acquired and liabilities assumed in acquisitions. These estimates may be adjusted as more current information becomes available, and any adjustment may be significant. As described in Note 2, Acquisitions, the acquired assets and liabilities of Square 1 were measured at their estimated fair values. We made significant estimates and exercised significant judgment in estimating fair values and accounting for such acquired assets and assumed liabilities. Reclassifications Certain prior period amounts have been reclassified to conform to the current period's presentation format. The operating segments previously reported have been aggregated to one segment to conform to the current period's presentation format.

Organization

PacWest Bancorp is a bank holding company registered under the Bank Holding Company Act of 1956, as amended. Our principal business is to serve as the holding company for our wholly-owned banking subsidiary, Pacific Western Bank. References to "Pacific Western" or the "Bank" refer to Pacific Western Bank together with its wholly-owned subsidiaries. References to “we,” "us," “our,” or the “Company,” refer to PacWest Bancorp together with its subsidiaries on a consolidated basis. When we refer to “PacWest” or to the holding company, we are referring to PacWest Bancorp, the parent company, on a stand‑alone basis. As of June 30, 2016, the Company had total assets of $21.1 billion, gross loans and leases of $14.7 billion, total deposits of $15.1 billion and total stockholders' equity of $4.5 billion.

We are focused on relationship-based business banking to small, middle-market and venture-backed businesses nationwide. The Bank offers a broad range of loan and lease and deposit products and services through 79 full-service branches located throughout the State of California, one branch located in Durham, North Carolina, and several loan production offices located in cities across the country. The Bank provides commercial banking services, including real estate, construction, and commercial loans and leases, and comprehensive deposit and treasury management services to small and middle-market businesses. Pacific Western offers additional products and services through its CapitalSource and Square 1 Bank divisions. CapitalSource provides cash flow, asset-based, equipment and real estate loans and treasury management services to established middle-market businesses on a national basis. Square 1 Bank offers a comprehensive suite of financial services focused on entrepreneurial businesses and their venture capital and private equity investors, with offices located in key innovation hubs across the United States. In addition, we provide investment advisory and asset management services to select clients through Square 1 Asset Management, Inc., a wholly-owned subsidiary of the Bank and a SEC-registered investment adviser. When we refer to "CapitalSource Inc." we are referring to the company acquired on April 7, 2014 and when we refer to the "CapitalSource Division" we are referring to a division of Pacific Western.

We generate our revenue primarily from interest received on loans and leases and, to a lesser extent, from interest received on investment securities, and fees received in connection with deposit services, extending credit and other services offered, including foreign exchange services. Our major operating expenses are compensation, occupancy, general operating expenses, and the interest paid by the Bank on deposits and borrowings.

We have completed 28 acquisitions from May 1, 2000 through June 30, 2016, including the acquisition of Square 1 Financial, Inc. on October 6, 2015. Our acquisitions have been accounted for using the acquisition method of accounting and, accordingly, the operating results of the acquired entities have been included in the consolidated financial statements from their respective acquisition dates. See Note 2. Acquisitions, for more information about the Square 1 acquisition.

On March 31, 2016, we sold our Pacific Western Equipment Finance ("PWEF") leasing unit in Midvale, Utah, including approximately $139 million of outstanding lease balances.

Significant Accounting Policies

Except as discussed below, our accounting policies are described in Note 1, Nature of Operations and Summary of Significant Accounting Policies, of our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2015 as filed with the Securities and Exchange Commission ("Form 10-K").

Basis of Presentation

Our interim consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Article 10 of Regulation S-X of the Securities Exchange Act of 1934. Accordingly, certain disclosures accompanying annual consolidated financial statements are omitted. In the opinion of management, all significant intercompany accounts and transactions have been eliminated and adjustments, consisting solely of normal recurring accruals and considered necessary for the fair presentation of financial statements for the interim periods, have been included. The current period's results of operations are not necessarily indicative of the results that ultimately may be achieved for the year. The interim consolidated financial statements and notes thereto should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Form 10-K.

Use of Estimates

We have made a number of estimates and assumptions related to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period to prepare these condensed consolidated financial statements in conformity with U.S. GAAP. Material estimates subject to change in the near term include, among other items, the allowance for credit losses, the carrying value and useful lives of intangible assets, the realization of deferred tax assets, and the fair value estimates of assets acquired and liabilities assumed in acquisitions. These estimates may be adjusted as more current information becomes available, and any adjustment may be significant.

As described in Note 2, Acquisitions, the acquired assets and liabilities of Square 1 were measured at their estimated fair values. We made significant estimates and exercised significant judgment in estimating fair values and accounting for such acquired assets and assumed liabilities.

Reclassifications

Certain prior period amounts have been reclassified to conform to the current period's presentation format. The operating segments previously reported have been aggregated to one segment to conform to the current period's presentation format.