Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Interest-earning deposits with banks	$ 434,867	$ 24,132
Debt Securities, Available-for-sale	5,210,134	3,746,142
Estimate of Fair Value Measurement
Assets
Cash and due from banks	218,899	223,541
Interest-earning deposits with banks	434,867	24,132
Debt Securities, Available-for-sale	5,210,134	3,746,172
FHLB stock	10,280	48,120
Loans held for sale	26,481	17,718
Loans	9,720,592	8,883,865
Interest Rate Cash Flow Hedge Asset at Fair Value		14,727
Liabilities
Time Deposits	338,815	397,736
FHLB Advances and FRB Borrowings	9,295	952,762
Repurchase agreements	73,859	64,437
Subordinated Debentures	35,414	35,491
Carrying Amount
Assets
Cash and due from banks	218,899	223,541
Interest-earning deposits with banks	434,867	24,132
Debt Securities, Available-for-sale	5,210,134	3,746,142
FHLB stock	10,280	48,120
Loans held for sale	26,481	17,718
Loans	9,278,520	8,659,497
Interest Rate Cash Flow Hedge Asset at Fair Value		14,727
Liabilities
Time Deposits	338,845	400,070
FHLB Advances and FRB Borrowings	7,414	953,469
Repurchase agreements	73,859	64,437
Subordinated Debentures	35,092	35,277
Fair Value, Inputs, Level 1 | Estimate of Fair Value Measurement
Assets
Cash and due from banks	218,899	223,541
Interest-earning deposits with banks	434,867	24,132
Debt Securities, Available-for-sale	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value		0
Liabilities
Time Deposits	0	0
FHLB Advances and FRB Borrowings	0	0
Repurchase agreements	0	0
Subordinated Debentures	0	0
Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Debt Securities, Available-for-sale	5,210,134	3,746,172
FHLB stock	10,280	48,120
Loans held for sale	26,481	17,718
Loans	0	0
Interest Rate Cash Flow Hedge Asset at Fair Value		14,727
Liabilities
Time Deposits	338,815	397,736
FHLB Advances and FRB Borrowings	9,295	952,762
Repurchase agreements	73,859	64,437
Subordinated Debentures	35,414	35,491
Fair Value, Inputs, Level 3 | Estimate of Fair Value Measurement
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Debt Securities, Available-for-sale	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	9,720,592	8,883,865
Interest Rate Cash Flow Hedge Asset at Fair Value		0
Liabilities
Time Deposits	0	0
FHLB Advances and FRB Borrowings	0	0
Repurchase agreements	0	0
Subordinated Debentures	0	0
Interest Rate Swap | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	46,184	19,144
Liabilities
Interest rate derivative liabilities, at fair value	46,637	19,145
Interest Rate Swap | Carrying Amount
Assets
Interest rate derivative assets, at fair value	46,184	19,144
Liabilities
Interest rate derivative liabilities, at fair value	46,637	19,145
Interest Rate Swap | Fair Value, Inputs, Level 1 | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	0	0
Liabilities
Interest rate derivative liabilities, at fair value	0	0
Interest Rate Swap | Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	46,184	19,144
Liabilities
Interest rate derivative liabilities, at fair value	46,637	19,145
Interest Rate Swap | Fair Value, Inputs, Level 3 | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	0	0
Liabilities
Interest rate derivative liabilities, at fair value	0	$ 0
Interest Rate Lock Commitments | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	1,096
Interest Rate Lock Commitments | Carrying Amount
Assets
Interest rate derivative assets, at fair value	1,096
Interest Rate Lock Commitments | Fair Value, Inputs, Level 1 | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	0
Interest Rate Lock Commitments | Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	0
Interest Rate Lock Commitments | Fair Value, Inputs, Level 3 | Estimate of Fair Value Measurement
Assets
Interest rate derivative assets, at fair value	1,096
Forward sales contracts | Estimate of Fair Value Measurement
Liabilities
Interest rate derivative liabilities, at fair value	165
Forward sales contracts | Carrying Amount
Liabilities
Interest rate derivative liabilities, at fair value	165
Forward sales contracts | Fair Value, Inputs, Level 1 | Estimate of Fair Value Measurement
Liabilities
Interest rate derivative liabilities, at fair value	0
Forward sales contracts | Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement
Liabilities
Interest rate derivative liabilities, at fair value	165
Forward sales contracts | Fair Value, Inputs, Level 3 | Estimate of Fair Value Measurement
Liabilities
Interest rate derivative liabilities, at fair value	$ 0