Organization	9 Months Ended
Organization	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	ORGANIZATION PacWest Bancorp, a Delaware corporation, is a bank holding company registered under the BHCA, with our corporate headquarters located in Beverly Hills, California. Our principal business is to serve as the holding company for our wholly-owned 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," 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. 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 74 full-service branches located in California, one branch located in Durham, North Carolina, and numerous loan production offices across the country through its Community Banking, National Lending and Venture Banking groups. Community Banking provides real estate loans, commercial loans, and comprehensive deposit and treasury management services to small and medium-sized businesses conducted primarily through our California-based branch offices. National Lending provides asset-based, equipment, and real estate loans and treasury management services to established middle-market businesses on a national basis. Venture Banking 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 Pacific Western Asset Management Inc., a wholly-owned subsidiary of the Bank and an SEC-registered investment adviser. 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 interest paid by the Bank on deposits and borrowings, compensation, occupancy, and general operating expenses. We have completed 29 acquisitions from May 1, 2000 through September 30, 2019. 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. Significant Accounting Policies 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, 2018 as filed with the Securities and Exchange Commission ("Form 10-K"). Accounting Standards Adopted in 2019 Effective January 1, 2019, the Company adopted ASU 2016-02, "Leases (Topic 842)," and the related amendments to this new standard issued in 2018. ASU 2016-02 supersedes Topic 840, “Leases,” and is intended to increase transparency and comparability among organizations by requiring the recognition of right-of-use (“ROU”) assets and lease liabilities by lessees for those leases classified as operating leases. Under the standard, disclosures are required to meet the objective of enabling users of the financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. The Company adopted the new standard using the optional transition method under ASU 2018-11, “Leases (Topic 842): Targeted Improvements,” and recognized a cumulative effect adjustment to increase retained earnings by $938,000, net of taxes, without restating prior periods and applying the requirements of the new standard prospectively. The Company has elected the following practical expedients: (1) to not separate lease and non-lease components for facilities leases; (2) to not reassess whether any expired or existing contracts are or contain leases and to maintain existing lease classifications; (3) to not record short-term leases (initial term less than 12 months) on the balance sheet; and (4) to present sales tax on a net basis for those transactions in which the Company is the lessor. The standard had a more significant impact on our condensed consolidated balance sheet than on our condensed consolidated statement of earnings. The most significant impact was the recognition of ROU assets and lease liabilities for operating leases, while the accounting for leases as a lessor remained substantially unchanged. The ROU asset is included within "Other assets," while the ROU liability is included within "Accrued interest payable and other liabilities". See Note 8. Leases and Note 7. Other Assets for further details. Effective January 1, 2019, the Company early-adopted any removed or modified disclosures as permitted by ASU 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework - Changes to Disclosure Requirements for Fair Value Measurements,” but will defer adoption of the additional disclosures until the effective date of January 1, 2020 as permitted in the transition guidance in ASU 2018-13. Effective January 1, 2019, the Company early-adopted ASU 2018-15, “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract (a consensus of the FASB Emerging Issues Task Force)," which aligns the requirements for capitalizing implementation costs in a cloud computing arrangement service contract with the requirements for capitalizing implementation costs incurred for an internal-use software license. The new guidance also prescribes the balance sheet, income statement, and cash flow classification of the capitalized implementation costs and related amortization expense, and requires additional quantitative and qualitative disclosures. The Company opted to apply ASU 2018-15 prospectively. The primary effect of the provisions is to capitalize eligible implementation costs during the application development phase and to amortize those costs over the life of the agreement. There was no impact to our condensed consolidated financial statements from the adoption of this new standard. Basis of Presentation Our interim condensed consolidated financial statements are prepared in accordance with 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 condensed 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. Actual results could differ from those estimates. Material estimates subject to change in the near term include, among other items, the allowance for credit losses (the combination of the allowance for loan and lease losses and the reserve for unfunded loan commitments), the carrying value 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. Reclassifications None.