Purchase Price Consideration (Details) - USD ($) $ in Thousands			12 Months Ended
		Nov. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Cash and due from banks			$ 202,427	$ 212,273
(amortized cost of $2,699,255 and $5,654,617, respectively)			2,346,864	4,843,487
Loans held for sale			122,757	65,076
Loans and leases, net	[1]		25,208,000	28,408,397
Premises and equipment, net			146,798	54,315
Other assets			1,131,249	1,012,007
Assets			38,534,064	41,228,936
Deposits			30,401,769	33,936,334
Long-Term Debt			2,911,322	$ 1,764,030
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net			464,377
Goodwill, Transfers			198,627
Pacific Western Bank
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Business Combination, Consideration Transferred		$ 663,004	663,004
Cash and due from banks			335,300
(amortized cost of $2,699,255 and $5,654,617, respectively)			872,800
Loans held for sale			2,182,988
Loans and leases, net			3,965,112
Premises and equipment, net			103,500
Other Intangible Assets, Net			145,500
Current and Deferred Tax Assets, net			209,100
Other assets			392,550
Assets		$ 8,405,477	8,206,850
Deposits			6,547,659
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances			794,000
Long-Term Debt			257,600
Other Liabilities			143,214
Liabilities Assumed			$ 7,742,473

[1] Excludes accrued interest receivable of $111.3 million and $124.3 million at December 31, 2023 and 2022, which is recorded in "Other assets" on the consolidated balance sheets.