Fair Value Measurements (Details 2) - USD ($) $ in Thousands		Jun. 30, 2021	Dec. 31, 2020
ASSETS
Debt Securities, Held-to-maturity		$ 861,821	$ 724,512
Held to Maturity, Fair Value, Total		877,801	752,177
Loans, net of allowance for credit losses (b)		8,836,631	9,279,474
Federal Home Loan Bank Stock		9,079	10,250
Bank Owned Life Insurance		242,963	200,525
LIABILITIES
Federal Home Loan Bank borrowings (f)		35,693	35,740
Long-term Debt	[1]	23,425	32,773
Long-term Debt, Fair Value	[1]	23,095	32,033
Subordinated Debt		49,743	49,696
Deposits [Member]
LIABILITIES
Time certificates of deposits (f)	[2]	11,169,652	10,042,541
Accrued Liabilities, Fair Value Disclosure	[2]	11,169,652	10,042,541
Time certificates of deposits (f)
LIABILITIES
Time certificates of deposits (f)	[1]	817,319	950,629
Accrued Liabilities, Fair Value Disclosure	[1]	819,067	955,598
Federal Home Loan Bank borrowings (f)
LIABILITIES
Federal Home Loan Bank borrowings (f)	[1]	35,693	35,740
Federal Home Loan Bank Borrowings, Fair Value Disclosure	[1]	35,723	35,885
Junior subordinated debentures (g)
LIABILITIES
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	[3]	62,852	62,851
Accrued Liabilities, Fair Value Disclosure	[3]	68,545	70,238
Subordinated debentures (f)
LIABILITIES
Subordinated Debt	[1]	49,743	49,696
Accrued Liabilities, Fair Value Disclosure	[1]	47,146	46,486
Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Debt [Member]
LIABILITIES
Long-term Debt, Fair Value	[1]	0	0
Significant Other Observable Inputs (Level 2) | Deposits [Member]
LIABILITIES
Accrued Liabilities, Fair Value Disclosure	[2]	11,169,652	10,042,541
Significant Other Observable Inputs (Level 2) | Time certificates of deposits (f)
LIABILITIES
Accrued Liabilities, Fair Value Disclosure	[1]	819,067	955,598
Significant Other Observable Inputs (Level 2) | Federal Home Loan Bank borrowings (f)
LIABILITIES
Federal Home Loan Bank Borrowings, Fair Value Disclosure	[1]	35,723	35,885
Significant Other Observable Inputs (Level 2) | Long-term Debt [Member]
LIABILITIES
Long-term Debt, Fair Value	[1]	23,095	32,033
Significant Other Observable Inputs (Level 2) | Junior subordinated debentures (g)
LIABILITIES
Accrued Liabilities, Fair Value Disclosure	[3]	68,545	70,238
Significant Unobservable Inputs (Level 3) | Long-term Debt [Member]
LIABILITIES
Long-term Debt, Fair Value	[1]	0	0
Significant Unobservable Inputs (Level 3) | Subordinated debentures (f)
LIABILITIES
Accrued Liabilities, Fair Value Disclosure	[1]	47,146	46,486
U.S. Government agency securities
ASSETS
Debt Securities, Held-to-maturity		33,853
Held to Maturity, Fair Value, Total		33,730
U.S. Government agency securities | Significant Other Observable Inputs (Level 2)
ASSETS
Held to Maturity, Fair Value, Total		33,730
U.S. treasury securities
ASSETS
Debt Securities, Held-to-maturity	[4]	3,010	4,017
Held to Maturity, Fair Value, Total	[4]	3,038	4,077
U.S. treasury securities | Significant Other Observable Inputs (Level 2)
ASSETS
Held to Maturity, Fair Value, Total	[4]	3,038	4,077
Agency mortgage-backed securities
ASSETS
Debt Securities, Held-to-maturity	[4]	381,030	356,085
Held to Maturity, Fair Value, Total	[4]	392,042	374,121
Agency mortgage-backed securities | Significant Other Observable Inputs (Level 2)
ASSETS
Held to Maturity, Fair Value, Total	[4]	392,042	374,121
Agency collateralized mortgage obligations
ASSETS
Debt Securities, Held-to-maturity	[4]	418,112	335,993
Held to Maturity, Fair Value, Total	[4]	421,841	344,119
Agency collateralized mortgage obligations | Significant Other Observable Inputs (Level 2)
ASSETS
Held to Maturity, Fair Value, Total	[4]	421,841	344,119
Single issuer trust preferred securities issued by banks
ASSETS
Debt Securities, Held-to-maturity	[4]	1,500	1,500
Held to Maturity, Fair Value, Total	[4]	1,508	1,498
Single issuer trust preferred securities issued by banks | Significant Other Observable Inputs (Level 2)
ASSETS
Held to Maturity, Fair Value, Total	[4]	1,508	1,498
Small Business Administration Pooled Securities [Member]
ASSETS
Debt Securities, Held-to-maturity	[4]	24,316	26,917
Held to Maturity, Fair Value, Total	[4]	25,642	28,362
Small Business Administration Pooled Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1)
ASSETS
Held to Maturity, Fair Value, Total	[4]	0	0
Small Business Administration Pooled Securities [Member] | Significant Other Observable Inputs (Level 2)
ASSETS
Held to Maturity, Fair Value, Total	[4]	25,642	28,362
Small Business Administration Pooled Securities [Member] | Significant Unobservable Inputs (Level 3)
ASSETS
Held to Maturity, Fair Value, Total	[4]	0	0
Loans, net of allowance for credit losses (b)
ASSETS
Loans, net of allowance for credit losses (b)	[5]	8,806,355	9,247,964
Loans Receivable, Fair Value Disclosure	[5]	8,782,780	9,253,381
Loans, net of allowance for credit losses (b) | Significant Unobservable Inputs (Level 3)
ASSETS
Loans Receivable, Fair Value Disclosure	[5]	8,782,780	9,253,381
Investment in Federal Home Loan Bank Stock [Member]
ASSETS
Federal Home Loan Bank Stock	[6]	9,079	10,250
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	9,079	10,250
Investment in Federal Home Loan Bank Stock [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1)
ASSETS
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	0	0
Investment in Federal Home Loan Bank Stock [Member] | Significant Other Observable Inputs (Level 2)
ASSETS
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	9,079	10,250
Investment in Federal Home Loan Bank Stock [Member] | Significant Unobservable Inputs (Level 3)
ASSETS
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	[6]	0	0
Cash Surrender Value [Member]
ASSETS
Cash Surrender Value, Fair Value Disclosure	[7]	242,963	200,525
Bank Owned Life Insurance	[7]	242,963	200,525
Cash Surrender Value [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1)
ASSETS
Cash Surrender Value, Fair Value Disclosure	[7]	0	0
Cash Surrender Value [Member] | Significant Other Observable Inputs (Level 2)
ASSETS
Cash Surrender Value, Fair Value Disclosure	[7]	242,963	200,525
Cash Surrender Value [Member] | Significant Unobservable Inputs (Level 3)
ASSETS
Cash Surrender Value, Fair Value Disclosure	[7]	$ 0	$ 0

[1] Fair value was determined by discounting anticipated future cash payments using rates currently available for instruments with similar remaining maturities.

[2] Fair value of demand deposits, savings and interest checking accounts and money market deposits is the amount payable on demand at the reporting date.

[3] Fair value was determined based upon market prices of securities with similar terms and maturities.

[4] The fair values presented are based on quoted market prices, where available. If quoted market prices are not available, fair values are based on quoted market prices of comparable instruments and/or discounted cash flow analysis.

[5] Fair value of loans is measured using the exit price valuation method, determined primarily by discounting the future cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities or cash flows, while incorporating liquidity and credit assumptions. Additionally, this amount excludes individually assessed collateral dependent loans, which are deemed to be marked to fair value on a nonrecurring basis.

[6] Federal Home Loan Bank stock has no quoted market value and is carried at cost; therefore the carrying amount approximates fair value.

[7] Cash surrender value of life insurance policies is recorded at its cash surrender value (or the amount that can be realized upon surrender of the policy), therefore, carrying amount approximates fair value.