Borrowings (Long-Term Obligations) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt Issuance Costs, Net	$ (3,459)	$ 0
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	10,000
2022	98,709
2023	125,500
2024	6,144
2025	7,500
Thereafter	1,000,310
Total long-term obligations	1,248,163	588,638
Trust Preferred Securities	128,500
Subordinated Debt [Member] \| Fixed-to-Floating subordinated notes at 3.375% maturing March 15, 2030
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 350,000	0
Debt interest rate	3.375%
Junior Subordinated Debt [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 132,500
Junior Subordinated Debt [Member] \| Junior subordinated debenture at 3-month LIBOR plus 1.75% maturing June 30, 2036
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 88,145	88,145
Junior Subordinated Debt [Member] \| Junior subordinated debenture at 3-month LIBOR plus 1.75% maturing June 30, 2036 \| Libor 3 Month Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%
Long-term Debt, Fiscal Year Maturity [Abstract]
Description of variable rate basis	3-month LIBOR
Junior Subordinated Debt [Member] \| Junior subordinated debenture at 3-month LIBOR plus 2.25% maturing June 15, 2034
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 19,588	19,588
Junior Subordinated Debt [Member] \| Junior subordinated debenture at 3-month LIBOR plus 2.25% maturing June 15, 2034 \| Libor 3 Month Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Long-term Debt, Fiscal Year Maturity [Abstract]
Description of variable rate basis	3-month LIBOR
Junior Subordinated Debt [Member] \| Junior subordinated debenture at 3-month LIBOR plus 2.85% maturing April 7, 2034
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 10,310	10,310
Junior Subordinated Debt [Member] \| Junior subordinated debenture at 3-month LIBOR plus 2.85% maturing April 7, 2034 \| Libor 3 Month Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.85%
Long-term Debt, Fiscal Year Maturity [Abstract]
Description of variable rate basis	3-month LIBOR
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 3-month LIBOR plus 2.80% maturing March 30, 2034
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 14,433	14,433
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 3-month LIBOR plus 2.80% maturing March 30, 2034 \| Libor 3 Month Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.80%
Long-term Debt, Fiscal Year Maturity [Abstract]
Description of variable rate basis	3-month LIBOR
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 7.00% maturing December 31, 2026(1)
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 20,000	20,000
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 7.00% maturing December 31, 2026(1) \| Libor 3 Month Rate [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt interest rate	7.00%
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 6.50% maturing October 1, 2025(2)
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 7,500	7,500
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 6.50% maturing October 1, 2025(2) \| Libor 3 Month Rate [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt interest rate	6.50%
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 7.13% called February 25, 2020(2)
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 0	5,000
Junior Subordinated Debt [Member] \| Junior subordinated debentures at 7.13% called February 25, 2020(2) \| Libor 3 Month Rate [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt interest rate	7.13%
Notes payable to FHLB of Atlanta \| Notes payable to FHLBs of Atlanta and Chicago with rates ranging from 0.75% to 2.99% and maturing through March 2032
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 655,175	317,191
Notes payable to FHLB of Atlanta \| Notes payable to FHLBs of Atlanta and Chicago with rates ranging from 0.75% to 2.99% and maturing through March 2032 \| Minimum
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt interest rate	0.75%
Notes payable to FHLB of Atlanta \| Notes payable to FHLBs of Atlanta and Chicago with rates ranging from 0.75% to 2.99% and maturing through March 2032 \| Maximum
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt interest rate	2.99%
Unsecured Term Loan [Member] \| Unsecured term loan at 1-month LIBOR plus 1.10% maturing September 5, 2022
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 82,125	96,425
Unsecured Term Loan [Member] \| Unsecured term loan at 1-month LIBOR plus 1.10% maturing September 5, 2022 \| Libor 1 Month Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.10%
Long-term Debt, Fiscal Year Maturity [Abstract]
Description of variable rate basis	1-month LIBOR
Capital Lease Obligations [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 6,308	8,230
Unamortized Purchase Accounting Adjustments [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	(1,999)	(1,569)
Other Long Term Debt [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total long-term obligations	$ 37	$ 3,385

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