Derivative Instruments (Narrative) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2020
Derivative [Line Items]
Derivative, Notional Amount		$ 5,027,916	$ 3,742,521
Derivative Asset	[1]	$ 112,182	60,492
Interest Rate Floor [Member]
Derivative [Line Items]
Derivative, Description of Terms		As of September 30, 2023, the Company held four interest rate floors indexed to 1-month SOFR to hedge the risk of declining interest rates on certain floating rate commercial loans. The floors have a combined notional value of $2.0 billion and are forward-starting. Each of the four interest rate floors has a six-year term and a notional amount of $500.0 million. In the event that the index rate falls below zero, the maximum rate that the Company can earn on the notional amount of each floor is limited to the strike rate.
Derivative, Notional Amount		$ 2,000,000	1,000,000
Derivative, Premium Paid		$ 90,200
Maximum Length of Time Hedged in Interest Rate Cash Flow Hedge		7 years
Unrealized gain (loss) on interest rate cash flow hedges, net of tax, amount recorded in accumulated other comprehensive income		$ 30,100
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		10,800
Monetized Interest Rate Floor [Member]
Derivative [Line Items]
Derivative, Notional Amount				$ 1,500,000
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months		22,600
Derivative Asset				$ 163,200
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred		$ 57,100
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimate of Time to Transfer		3 years 2 months 12 days
Interest rate swaps
Derivative [Line Items]
Derivative, Notional Amount		$ 2,199,242	1,981,821
Variation Margin Impact to Positive Fair Values of Cleared Swaps		0	$ (27,800)
August 2023 Interest Rate Floors
Derivative [Line Items]
Derivative, Premium Paid		28,500
February 23, 2023
Derivative [Line Items]
Derivative, Premium Paid		$ 25,900

[1] * The fair value of each class of derivative is shown in Note 11.