Summary of Significant Accounting Policies - Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment Securities - Held to Maturity	$ 2,348,528	$ 2,487,440
Accrued interest receivable (AIR)	$ 132,700	$ 127,000
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other Assets.	Other Assets.
Net book balance	$ 1,000
Liability recorded for expected credit losses on unfunded commitments	$ 50,200
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reasonable and supportable forecast period	1 year
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reasonable and supportable forecast period	2 years
Other Assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accrued interest receivable for investment securities	$ 25,800	$ 26,500
Other Liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Liability recorded for expected credit losses on unfunded commitments	$ 50,200	$ 56,300