Borrowings and Subordinated Debentures - Subordinated Debentures (Details) $ in Thousands, € in Millions		6 Months Ended
		Jun. 30, 2023 USD ($)		Jun. 30, 2023 EUR (€)		Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Subordinated Borrowing [Line Items]
Subordinated Debentures, Gross		$ 935,297					$ 934,514
Subordinated debt		$ 870,378					$ 867,087
Rate		5.46%		5.46%			5.36%
Debt Issuance Costs, Gross		$ (4,600)				$ (17,900)
Trust Preferred Securities Two Thousand Six Series Three
Subordinated Borrowing [Line Items]
Denomination value | €				€ 25.8
Subordinated notes due May 2031
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		2.52%
Euribor Rate | Trust Preferred Securities Two Thousand Six Series Three
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		2.05%
LIBOR | Subordinated Debt Trust V Due September 2033
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		3.10%
LIBOR | Subordinated Debt Trust VI Due September 2033
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		3.05%
LIBOR | Subordinated Debt Trust CII Due September 2033
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		2.95%
LIBOR | Subordinated Debt Trust VII Due April 2034
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		2.75%
LIBOR | Subordinated Debt Trust CIII Due September 2035
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.69%
LIBOR | Subordinated Debt Trust FCCI Due March 2037
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.60%
LIBOR | Subordinated Debt Trust FCBI Due December 2035
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.55%
LIBOR | Trust Preferred Securities Two Thousand Five Series One
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
LIBOR | Trust Preferred Securities Two Thousand Five Series Two
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
LIBOR | Two Thousand Six One Term Debt Securitization
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
LIBOR | Two Thousand Six Two Term Debt Securitization
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
LIBOR | Trust Preferred Securities Two Thousand Six Series Four
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
LIBOR | Trust Preferred Securities Two Thousand Six Series Five
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
LIBOR | Two Thousand Seven One Term Debt Securitization
Subordinated Borrowing [Line Items]
Rate Index (Quarterly Reset)		1.95%
Subordinated Debentures
Subordinated Borrowing [Line Items]
Unamortized discount	[1]	$ (64,919)					$ (67,427)
Rate		5.60%	[2]	5.60%	[2]		5.08%
Subordinated Debentures | Subordinated Debt Trust V Due September 2033
Subordinated Borrowing [Line Items]
Balance		$ 10,310					$ 10,310
Rate		8.61%	[2]	8.61%	[2]		7.84%
Subordinated Debentures | Subordinated Debt Trust VI Due September 2033
Subordinated Borrowing [Line Items]
Balance		$ 10,310					$ 10,310
Rate		8.60%	[2]	8.60%	[2]		7.82%
Subordinated Debentures | Subordinated Debt Trust CII Due September 2033
Subordinated Borrowing [Line Items]
Balance		$ 5,155					$ 5,155
Rate		8.46%	[2]	8.46%	[2]		7.69%
Subordinated Debentures | Subordinated Debt Trust VII Due April 2034
Subordinated Borrowing [Line Items]
Balance		$ 61,856					$ 61,856
Rate		8.05%	[2]	8.05%	[2]		7.16%
Subordinated Debentures | Subordinated Debt Trust CIII Due September 2035
Subordinated Borrowing [Line Items]
Balance		$ 20,619					$ 20,619
Rate		7.24%	[2]	7.24%	[2]		6.46%
Subordinated Debentures | Subordinated Debt Trust FCCI Due March 2037
Subordinated Borrowing [Line Items]
Balance		$ 16,495					$ 16,495
Rate		7.15%	[2]	7.15%	[2]		6.37%
Subordinated Debentures | Subordinated Debt Trust FCBI Due December 2035
Subordinated Borrowing [Line Items]
Balance		$ 10,310					$ 10,310
Rate		7.10%	[2]	7.10%	[2]		6.32%
Subordinated Debentures | Trust Preferred Securities Two Thousand Five Series One
Subordinated Borrowing [Line Items]
Balance		$ 82,475					$ 82,475
Rate		7.50%	[2]	7.50%	[2]		6.72%
Subordinated Debentures | Trust Preferred Securities Two Thousand Five Series Two
Subordinated Borrowing [Line Items]
Balance		$ 128,866					$ 128,866
Rate		7.25%	[2]	7.25%	[2]		6.36%
Subordinated Debentures | Two Thousand Six One Term Debt Securitization
Subordinated Borrowing [Line Items]
Balance		$ 51,545					$ 51,545
Rate		7.25%	[2]	7.25%	[2]		6.36%
Subordinated Debentures | Two Thousand Six Two Term Debt Securitization
Subordinated Borrowing [Line Items]
Balance		$ 51,550					$ 51,550
Rate		7.25%	[2]	7.25%	[2]		6.36%
Subordinated Debentures | Trust Preferred Securities Two Thousand Six Series Three
Subordinated Borrowing [Line Items]
Balance	[3]	$ 28,118					$ 27,592
Rate		5.30%	[2]	5.30%	[2]		3.66%
Subordinated Debentures | Trust Preferred Securities Two Thousand Six Series Four
Subordinated Borrowing [Line Items]
Balance		$ 16,470					$ 16,470
Rate		7.25%	[2]	7.25%	[2]		6.36%
Subordinated Debentures | Trust Preferred Securities Two Thousand Six Series Five
Subordinated Borrowing [Line Items]
Balance		$ 6,650					$ 6,650
Rate		7.25%	[2]	7.25%	[2]		6.36%
Subordinated Debentures | Two Thousand Seven One Term Debt Securitization
Subordinated Borrowing [Line Items]
Balance		$ 39,177					$ 39,177
Rate		7.25%	[2]	7.25%	[2]		6.36%
Subordinated Debentures | Subordinated notes due May 2031
Subordinated Borrowing [Line Items]
Balance		$ 395,391	[4]				$ 395,134
Rate		3.25%	[2]	3.25%	[2]		3.25%

[1] Amount represents the fair value adjustment on trust preferred securities assumed in acquisitions.(6)    On July 1, 2023, interest rate will transition to term SOFR plus the relevant spread adjustment as the applicable benchmark upon the cessation of LIBOR on June 30, 2023.

[2] Rates do not include the effects of discounts and issuance costs.

[3] Denomination is in Euros with a value of €25.8 million.

[4] Net of unamortized issuance costs of $4.6 million.