Investment Securities - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Investment securities:
Available-for-sale:
Amount Outstanding	$ 4,806,727	$ 3,819,376
Unamortized Premium/(Discount)	0	0
Amortized cost	4,769,426	3,834,714
Allowance for losses	(33)	(52)
Unrealized Gains	4,703	12,203
Unrealized Losses	(194,532)	(10,474)
Fair Value	4,579,564	3,836,391
Held-to-maturity:
Amount Outstanding	45,032	44,970
Unamortized Premium/(Discount)	0	0
Amortized Cost	45,032	44,970
Allowance for losses	0	0
Unrealized Gains	2,433	1,612
Unrealized Losses	0	0
Fair Value	47,465	46,582
Available-for-sale, accrued interest excluded	10,600	4,300
Available-for-Sale Securities \| Investment securities:
Available-for-sale:
Unamortized Premium/(Discount)	(37,301)	15,338
Held-to-maturity:
Unamortized Premium/(Discount)	(37,301)	15,338
Floating Interest Rate \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Available-for-sale:
Amount Outstanding	19,700	19,700
Amortized cost	19,700	19,700
Allowance for losses	(33)	(52)
Unrealized Gains	0	0
Unrealized Losses	(640)	(394)
Fair Value	19,027	19,254
Floating Interest Rate \| Guaranteed mortgage-backed securities
Available-for-sale:
Amount Outstanding	2,433,696	2,168,016
Amortized cost	2,433,496	2,168,106
Allowance for losses	0	0
Unrealized Gains	1,954	11,821
Unrealized Losses	(42,910)	(1,096)
Fair Value	2,392,540	2,178,831
Floating Interest Rate \| Available-for-Sale Securities \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Available-for-sale:
Unamortized Premium/(Discount)	0	0
Held-to-maturity:
Unamortized Premium/(Discount)	0	0
Floating Interest Rate \| Available-for-Sale Securities \| Guaranteed mortgage-backed securities
Available-for-sale:
Unamortized Premium/(Discount)	(200)	90
Held-to-maturity:
Unamortized Premium/(Discount)	(200)	90
Fixed Interest Rate \| Guaranteed mortgage-backed securities
Available-for-sale:
Amount Outstanding	1,207,416	451,660
Amortized cost	1,177,095	464,185
Allowance for losses	0	0
Unrealized Gains	2,128	382
Unrealized Losses	(130,837)	(5,730)
Fair Value	1,048,386	458,837
Held-to-maturity:
Amount Outstanding	45,032	44,970
Amortized Cost	45,032	44,970
Allowance for losses	0	0
Unrealized Gains	2,433	1,612
Unrealized Losses	0	0
Fair Value	$ 47,465	$ 46,582
Held-to-maturity investment securities weighted average yield	4.50%	1.50%
Fixed Interest Rate \| Fixed rate U.S. Treasuries
Available-for-sale:
Amount Outstanding	$ 1,145,915	$ 1,180,000
Amortized cost	1,139,135	1,182,723
Allowance for losses	0	0
Unrealized Gains	621	0
Unrealized Losses	(20,145)	(3,254)
Fair Value	1,119,611	1,179,469
Fixed Interest Rate \| Available-for-Sale Securities \| Guaranteed mortgage-backed securities
Available-for-sale:
Unamortized Premium/(Discount)	(30,321)	12,525
Held-to-maturity:
Unamortized Premium/(Discount)	(30,321)	12,525
Fixed Interest Rate \| Available-for-Sale Securities \| Fixed rate U.S. Treasuries
Available-for-sale:
Unamortized Premium/(Discount)	(6,780)	2,723
Held-to-maturity:
Unamortized Premium/(Discount)	(6,780)	2,723
Fixed Interest Rate \| Held-to-Maturity Securities \| Guaranteed mortgage-backed securities
Available-for-sale:
Unamortized Premium/(Discount)	0	0
Held-to-maturity:
Unamortized Premium/(Discount)	$ 0	$ 0

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