Securities - Gross Unrealized Losses and Fair Value by Investment Category (Details) $ in Thousands	Sep. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Available for Sale:
Number of positions, Less than 12 Months \| security	53	79
Fair Value, Less than 12 Months	$ 113,786	$ 331,023
Unrealized Losses, Less than 12 Months	$ (950)	$ (2,394)
Number of positions, 12 Months or More \| security	4	22
Fair value, 12 Months or More	$ 9,532	$ 33,700
Unrealized Losses, 12 Months or More	$ (3,553)	$ (2,484)
Number of positions \| security	57	101
Fair Value	$ 123,318	$ 364,723
Unrealized Losses	$ (4,503)	$ (4,878)
Obligations of other U.S. Government agencies and corporations
Available for Sale:
Number of positions, Less than 12 Months \| security		0
Fair Value, Less than 12 Months		$ 0
Unrealized Losses, Less than 12 Months		$ 0
Number of positions, 12 Months or More \| security		1
Fair value, 12 Months or More		$ 1,008
Unrealized Losses, 12 Months or More		$ (3)
Number of positions \| security		1
Fair Value		$ 1,008
Unrealized Losses		$ (3)
Obligations of states and political subdivisions
Available for Sale:
Number of positions, Less than 12 Months \| security	28	26
Fair Value, Less than 12 Months	$ 45,111	$ 33,902
Unrealized Losses, Less than 12 Months	$ (651)	$ (365)
Number of positions, 12 Months or More \| security	0	0
Fair value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of positions \| security	28	26
Fair Value	$ 45,111	$ 33,902
Unrealized Losses	$ (651)	$ (365)
Trust preferred securities
Available for Sale:
Number of positions, Less than 12 Months \| security	0	0
Fair Value, Less than 12 Months	$ 0	$ 0
Unrealized Losses, Less than 12 Months	$ 0	$ 0
Number of positions, 12 Months or More \| security	2	2
Fair value, 12 Months or More	$ 8,492	$ 9,986
Unrealized Losses, 12 Months or More	$ (3,550)	$ (2,167)
Number of positions \| security	2	2
Fair Value	$ 8,492	$ 9,986
Unrealized Losses	$ (3,550)	$ (2,167)
Other debt securities
Available for Sale:
Number of positions, Less than 12 Months \| security	12	3
Fair Value, Less than 12 Months	$ 14,833	$ 8,737
Unrealized Losses, Less than 12 Months	$ (128)	$ (131)
Number of positions, 12 Months or More \| security	1	1
Fair value, 12 Months or More	$ 575	$ 741
Unrealized Losses, 12 Months or More	$ (3)	$ (1)
Number of positions \| security	13	4
Fair Value	$ 15,408	$ 9,478
Unrealized Losses	$ (131)	$ (132)
Government agency mortgage backed securities \| Residential mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	3	37
Fair Value, Less than 12 Months	$ 21,244	$ 233,179
Unrealized Losses, Less than 12 Months	$ (64)	$ (1,504)
Number of positions, 12 Months or More \| security	0	16
Fair value, 12 Months or More	$ 0	$ 20,775
Unrealized Losses, 12 Months or More	$ 0	$ (312)
Number of positions \| security	3	53
Fair Value	$ 21,244	$ 253,954
Unrealized Losses	$ (64)	$ (1,816)
Government agency mortgage backed securities \| Commercial mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	1	1
Fair Value, Less than 12 Months	$ 1,546	$ 4,976
Unrealized Losses, Less than 12 Months	$ (1)	$ (23)
Number of positions, 12 Months or More \| security	1	2
Fair value, 12 Months or More	$ 465	$ 1,190
Unrealized Losses, 12 Months or More	$ 0	$ (1)
Number of positions \| security	2	3
Fair Value	$ 2,011	$ 6,166
Unrealized Losses	$ (1)	$ (24)
Government agency collateralized mortgage obligations \| Residential mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	6	11
Fair Value, Less than 12 Months	$ 18,206	$ 45,319
Unrealized Losses, Less than 12 Months	$ (29)	$ (262)
Number of positions, 12 Months or More \| security	0	0
Fair value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of positions \| security	6	11
Fair Value	$ 18,206	$ 45,319
Unrealized Losses	$ (29)	$ (262)
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	3	1
Fair Value, Less than 12 Months	$ 12,846	$ 4,910
Unrealized Losses, Less than 12 Months	$ (77)	$ (109)
Number of positions, 12 Months or More \| security	0	0
Fair value, 12 Months or More	$ 0	$ 0
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of positions \| security	3	1
Fair Value	$ 12,846	$ 4,910
Unrealized Losses	$ (77)	$ (109)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without an allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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