Stockholders' Equity	3 Months Ended
Stockholders' Equity	Jun. 30, 2022
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	STOCKHOLDERS' EQUITY Stock-Based Compensation At the annual meeting of stockholders held on May 11, 2021, the Company's stockholders approved the Amended and Restated PacWest Bancorp 2017 Stock Incentive Plan (the “Amended and Restated 2017 Plan”). The Company’s Amended and Restated 2017 Plan permits stock-based compensation awards to officers, directors, employees, and consultants and will remain in effect until December 31, 2026. The Amended and Restated 2017 Plan authorizes grants of stock-based compensation instruments to issue up to 6,650,000 shares. As of June 30, 2022, there were 2,083,271 shares available for grant under the Amended and Restated 2017 Plan. Restricted Stock Restricted stock amortization totaled $9.0 million and $8.2 million for the three months ended June 30, 2022 and 2021 and $16.5 million and $14.6 million for the six months ended June 30, 2022 and 2021. Such amounts are included in "Compensation expense" on the condensed consolidated statements of earnings. The amount of unrecognized compensation expense related to unvested TRSAs and PRSUs as of June 30, 2022 totaled $82.3 million. Time-Based Restricted Stock Awards At June 30, 2022, there were 2,516,279 shares of unvested TRSAs outstanding. TRSAs generally vest ratably over a service period of three or four years from the date of the grant or immediately upon death of an employee. Compensation expense related to TRSAs is based on the fair value of the underlying award on the grant date and is recognized over the vesting period using the straight-line method. Performance-Based Restricted Stock Units At June 30, 2022, there were 505,647 units of unvested PRSUs that have been granted. The PRSUs will vest only if performance goals with respect to certain financial metrics are met over a three-year performance period. The shares underlying the PRSUs are not considered issued and outstanding until they vest. PRSUs are granted and initially expensed based on a target number. The number of shares that will ultimately vest based on actual performance will range from zero to a maximum of either 150% or 200% of target. Compensation expense related to PRSUs is based on the fair value of the underlying award on the grant date and is amortized over the vesting period using the straight-line method unless it is determined that: (1) attainment of the financial metrics is less than probable, in which case a portion or all of the amortization is suspended, or (2) attainment of the financial metrics is improbable, in which case a portion or all of the previously recognized amortization is reversed and also suspended. If it is determined that attainment of a financial measure higher than target is probable, the amortization will increase to up to 150% or 200% of the target amortization amount. Annual PRSU expense may vary during the three-year performance period based upon changes in management's estimate of the number of shares that may ultimately vest. In the case where the performance target for the PRSU is based on a market condition (such as total shareholder return), the amortization is neither reversed nor suspended if it is subsequently determined that the attainment of the performance target is less than probable or improbable and the employee continues to meet the service requirement of the award. Preferred Stock Issuance On June 6, 2022, the Company issued and sold 20,530,000 depositary shares (the “Depositary Shares”), each representing a 1/40th ownership interest in a share of the Company’s 7.75% fixed rate reset non-cumulative, non-convertible, perpetual preferred stock, Series A, par value $0.01 per share (the “Series A preferred stock”), with a liquidation preference of $1,000 per share of Series A preferred stock (equivalent to $25.00 per Depositary Share). The Series A preferred stock qualifies as Tier 1 capital for purposes of regulatory capital calculations. The gross proceeds were $513.3 million while net proceeds from the issuance of the Series A preferred stock, after deducting $14.7 million of offering costs including the underwriting discount and other expenses, were $498.5 million. Holders of the Depositary Shares will be entitled to all proportional rights and preferences of the Series A preferred stock (including dividend, voting, redemption, and liquidation rights). Dividends on the Series A preferred stock will not be cumulative or mandatory. If the Company’s board of directors does not declare a dividend on the Series A preferred stock in respect of a dividend period, then no dividend shall be deemed to be payable for such dividend period, or be cumulative, and the Company will have no obligation to pay any dividend for that dividend period, whether or not the board of directors, declares a dividend on the Series A preferred stock or any other class or series of its capital stock for any future dividend period. Additionally, so long as any share of Series A preferred stock remains outstanding, unless dividends on all outstanding shares of Series A preferred stock for the most recently completed dividend period have been paid in full or declared and a sum sufficient for the payment thereof has been set aside for payment, no dividend shall be declared or paid or set aside for payment and no distribution shall be declared or made or set aside for payment on the Company’s common stock. The Series A preferred stock is perpetual and has no maturity date. The Series A preferred stock is not subject to any mandatory redemption, sinking fund, or other similar provisions. The Company, at its option and subject to prior regulatory approval, may redeem the Series A preferred stock (i) in whole or in part, from time to time, on any dividend payment date on or after September 1, 2027 or (ii) in whole but not in part at any time within 90 days following a regulatory capital treatment event, in each case, at a redemption price equal to $1,000 per share of Series A preferred stock (equivalent to $25 per Depositary Share), plus any declared and unpaid dividends, without regard to any undeclared dividends, to but excluding the redemption date. Neither the holders of the Series A preferred stock nor holders of the Depositary Shares will have the right to require the redemption or repurchase of the Series A preferred stock.