Subsequent Events	9 Months Ended
Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Square 1 Financial, Inc. Acquisition On October 6, 2015, PacWest completed the acquisition of Square 1 Financial, Inc. ("Square 1"). As part of the acquisition, Square 1 Bank, a wholly-owned subsidiary of Square 1, merged with and into PacWest's wholly-owned banking subsidiary, Pacific Western Bank, and the surviving subsidiary bank is Pacific Western Bank. As of September 30, 2015, Square 1 had $4.0 billion in assets. Upon closing, we formed the Square 1 Bank Division of Pacific Western Bank. The Square 1 Bank Division will continue its nationwide focus on venture-backed companies and venture capital firms, and will continue to offer a full spectrum of deposit, treasury management, and lending products. Under the terms of the definitive agreement, Square 1 stockholders received 0.5597 of a share of PacWest common stock for each share of Square 1 common stock and holders of stock options and restricted stock units received cash consideration as described in the agreement. PacWest issued an aggregate of approximately 18.1 million shares of PacWest common stock to Square 1 stockholders and a total of $17.8 million to Square 1 equity award holders in satisfaction of all outstanding equity awards. Based on the closing price of PacWest's common stock on October 6, 2015 of $43.97 per share, the aggregate consideration paid to Square 1 common stockholders and holders of equity awards to acquire Square 1 common stock was approximately $815 million. Former holders of Square 1 common stock as a group received shares of PacWest common stock in the acquisition constituting approximately 15.0% of the outstanding shares of PacWest common stock immediately after the acquisition. Square 1 Bank was a commercial bank headquartered in Durham, North Carolina. Square 1 Bank offered a comprehensive suite of financial services focused on entrepreneurial businesses and their venture capital and private equity investors, with offices located in all key innovative hubs across the United States. We completed the acquisition to improve our core deposits, expand the Company's nationwide lending platform, and increase the Company's presence in the technology and life-sciences credit markets. As of September 30, 2015, on a pro forma combined basis with Square 1 and excluding purchase accounting adjustments, PacWest would have had approximately $21 billion in assets with 80 branches throughout California and one branch in North Carolina. Common Stock Dividends On November 2, 2015, the Company announced that the Board of Directors had declared a quarterly cash dividend of $0.50 per common share. The cash dividend is payable on November 30, 2015 to stockholders of record at the close of business on November 16, 2015. We have evaluated events that have occurred subsequent to September 30, 2015 and have concluded there are no other subsequent events that would require recognition in the accompanying consolidated financial statements.

Subsequent Events

Square 1 Financial, Inc. Acquisition

On October 6, 2015, PacWest completed the acquisition of Square 1 Financial, Inc. ("Square 1"). As part of the acquisition, Square 1 Bank, a wholly-owned subsidiary of Square 1, merged with and into PacWest's wholly-owned banking subsidiary, Pacific Western Bank, and the surviving subsidiary bank is Pacific Western Bank. As of September 30, 2015, Square 1 had $4.0 billion in assets.

Upon closing, we formed the Square 1 Bank Division of Pacific Western Bank. The Square 1 Bank Division will continue its nationwide focus on venture-backed companies and venture capital firms, and will continue to offer a full spectrum of deposit, treasury management, and lending products.

Under the terms of the definitive agreement, Square 1 stockholders received 0.5597 of a share of PacWest common stock for each share of Square 1 common stock and holders of stock options and restricted stock units received cash consideration as described in the agreement. PacWest issued an aggregate of approximately 18.1 million shares of PacWest common stock to Square 1 stockholders and a total of $17.8 million to Square 1 equity award holders in satisfaction of all outstanding equity awards. Based on the closing price of PacWest's common stock on October 6, 2015 of $43.97 per share, the aggregate consideration paid to Square 1 common stockholders and holders of equity awards to acquire Square 1 common stock was approximately $815 million. Former holders of Square 1 common stock as a group received shares of PacWest common stock in the acquisition constituting approximately 15.0% of the outstanding shares of PacWest common stock immediately after the acquisition.

Square 1 Bank was a commercial bank headquartered in Durham, North Carolina. Square 1 Bank offered a comprehensive suite of financial services focused on entrepreneurial businesses and their venture capital and private equity investors, with offices located in all key innovative hubs across the United States. We completed the acquisition to improve our core deposits, expand the Company's nationwide lending platform, and increase the Company's presence in the technology and life-sciences credit markets.

As of September 30, 2015, on a pro forma combined basis with Square 1 and excluding purchase accounting adjustments, PacWest would have had approximately $21 billion in assets with 80 branches throughout California and one branch in North Carolina.

Common Stock Dividends

On November 2, 2015, the Company announced that the Board of Directors had declared a quarterly cash dividend of $0.50 per common share. The cash dividend is payable on November 30, 2015 to stockholders of record at the close of business on November 16, 2015.

We have evaluated events that have occurred subsequent to September 30, 2015 and have concluded there are no other subsequent events that would require recognition in the accompanying consolidated financial statements.