Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
		Nov. 30, 2023	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Earnings Per Share [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic			$ (1,938,925)	$ 404,274		$ 606,959
Weighted Average Number of Shares Issued, Basic			86,563,000	78,875,000	[1]	78,400,000	[1]
Weighted Average Number of Shares, Restricted Stock			(1,169,407)	(1,604,412)	[2]	(1,481,061)	[2]
Weighted Average Number of Shares Outstanding, Basic, Total			85,394,000	77,271,000		76,919,000
Basic income per share (usd per share)			$ (22.71)	$ 5.14		$ 7.76
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (1,938,925)	$ 396,800		$ 596,711
Diluted income per share (usd per share)			$ (22.71)	$ 5.14		$ 7.76
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic			$ (1,938,925)	$ 404,274		$ 606,959
Allocated to Common and Equivalent Shares	[3]			(7,474)		(10,248)
Undistributed Earnings, Basic			$ (1,938,925)	$ 396,800		$ 596,711
Weighted Average Number of Shares Issued, Basic			86,563,000	78,875,000	[1]	78,400,000	[1]
Weighted Average Number of Shares, Restricted Stock			1,169,407	1,604,412	[2]	1,481,061	[2]
Weighted Average Number of Shares Outstanding, Basic			85,394,000	77,271,000		76,919,000
Basic income per share (usd per share)			$ (22.71)	$ 5.14		$ 7.76
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (1,938,925)	$ 396,800		$ 596,711
Weighted Average Number of Shares Outstanding, Diluted			85,394,000	77,271,000	[1]	76,919,000	[1]
Earnings Per Share, Diluted			$ (22.71)	$ 5.14		$ 7.76
Pacific Western Bank
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock Issued During Period, Shares, Acquisitions		0.6569
Voting Common Stock | Common Stock
Earnings Per Share [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic			$ (1,917,121)
Weighted Average Number of Shares Issued, Basic			85,603,000
Weighted Average Number of Shares, Restricted Stock			1,169,000
Weighted Average Number of Shares Outstanding, Basic, Total			84,434,000
Basic income per share (usd per share)			$ (22.71)
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (1,917,121)
Diluted income per share (usd per share)			$ (22.71)
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic			$ (1,917,121)
Undistributed Earnings, Basic			$ (1,917,121)
Weighted Average Number of Shares Issued, Basic			85,603,000
Weighted Average Number of Shares, Restricted Stock			(1,169,000)
Weighted Average Number of Shares Outstanding, Basic			84,434,000
Basic income per share (usd per share)			$ (22.71)
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (1,917,121)
Weighted Average Number of Shares Outstanding, Diluted			84,434,000
Earnings Per Share, Diluted			$ (22.71)
Nonvoting Common Stock | Common Stock
Earnings Per Share [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic			$ (20,884)
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic			(20,884)
Undistributed Earnings, Basic			(20,884)
Class B Non-Voting | Common Stock
Earnings Per Share [Abstract]
Net Income (Loss) Available to Common Stockholders, Basic			$ (920)
Weighted Average Number of Shares Issued, Basic			40,000
Weighted Average Number of Shares, Restricted Stock			0
Weighted Average Number of Shares Outstanding, Basic, Total			40,000
Basic income per share (usd per share)			$ (22.71)
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (920)
Diluted income per share (usd per share)			$ (22.71)
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic			$ (920)
Undistributed Earnings, Basic			$ (920)
Weighted Average Number of Shares Issued, Basic			40,000
Weighted Average Number of Shares, Restricted Stock			0
Weighted Average Number of Shares Outstanding, Basic			40,000
Basic income per share (usd per share)			$ (22.71)
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (920)
Weighted Average Number of Shares Outstanding, Diluted			40,000
Earnings Per Share, Diluted			$ (22.71)
Non-Voting Common Stock Equivalents | Common Stock
Earnings Per Share [Abstract]
Weighted Average Number of Shares Issued, Basic			920,000
Weighted Average Number of Shares, Restricted Stock			0
Weighted Average Number of Shares Outstanding, Basic, Total			920,000
Basic income per share (usd per share)			$ (22.71)
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (20,884)
Diluted income per share (usd per share)			$ (22.71)
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Issued, Basic			920,000
Weighted Average Number of Shares, Restricted Stock			0
Weighted Average Number of Shares Outstanding, Basic			920,000
Basic income per share (usd per share)			$ (22.71)
Net Income Loss From Continuing Operation Available To Common Stockholders Basic			$ (20,884)
Weighted Average Number of Shares Outstanding, Diluted			920,000
Earnings Per Share, Diluted			$ (22.71)

[1] Share amounts for 2022 and 2021 have been restated by multiplying historical amounts by the Merger exchange ratio of 0.6569

[2] Share amounts for 2022 and 2021 have been restated by multiplying historical amounts by the Merger exchange ratio of 0.6569.

[3] Represents cash dividends paid to holders of unvested restricted stock, net of forfeitures, plus undistributed earnings amounts available to holders of unvested restricted stock, if any.