Securities - Gross Unrealized Losses and Fair Value by Investment Category (Details) $ in Thousands	Jun. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Available for Sale:
Number of positions, Less than 12 Months \| security	71	21
Fair Value, Less than 12 Months	$ 789,279	$ 75,359
Unrealized Losses, Less than 12 Months	$ (6,310)	$ (211)
Number of positions, 12 Months or More \| security	15	4
Fair value, 12 Months or More	$ 118,045	$ 10,037
Unrealized Losses, 12 Months or More	$ (1,582)	$ (3,004)
Number of positions \| security	86	25
Fair Value	$ 907,324	$ 85,396
Unrealized Losses	$ (7,892)	$ (3,215)
Obligations of states and political subdivisions
Available for Sale:
Number of positions, Less than 12 Months \| security	20	6
Fair Value, Less than 12 Months	$ 40,176	$ 9,403
Unrealized Losses, Less than 12 Months	$ (414)	$ (45)
Number of positions, 12 Months or More \| security	1	0
Fair value, 12 Months or More	$ 2,166	$ 0
Unrealized Losses, 12 Months or More	$ (11)	$ 0
Number of positions \| security	21	6
Fair Value	$ 42,342	$ 9,403
Unrealized Losses	$ (425)	$ (45)
Trust preferred securities
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		2
Fair value, 12 Months or More		$ 9,012
Unrealized Losses, 12 Months or More		$ (3,001)
Number of positions \| security		2
Fair Value		$ 9,012
Unrealized Losses		$ (3,001)
Other debt securities
Available for Sale:
Number of positions, Less than 12 Months \| security	1	4
Fair Value, Less than 12 Months	$ 1,000	$ 3,330
Unrealized Losses, Less than 12 Months	$ 0	$ (70)
Number of positions, 12 Months or More \| security	0	1
Fair value, 12 Months or More	$ 0	$ 566
Unrealized Losses, 12 Months or More	$ 0	$ (3)
Number of positions \| security	1	5
Fair Value	$ 1,000	$ 3,896
Unrealized Losses	$ 0	$ (73)
Government agency mortgage backed securities \| Residential mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	25	2
Fair Value, Less than 12 Months	$ 210,509	$ 19,755
Unrealized Losses, Less than 12 Months	$ (1,572)	$ (23)
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	25	2
Fair Value	$ 210,509	$ 19,755
Unrealized Losses	$ (1,572)	$ (23)
Government agency mortgage backed securities \| Commercial mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	0	1
Fair Value, Less than 12 Months	$ 0	$ 1,538
Unrealized Losses, Less than 12 Months	$ 0	$ (1)
Number of positions, 12 Months or More \| security	1	1
Fair value, 12 Months or More	$ 446	$ 459
Unrealized Losses, 12 Months or More	$ 0	$ 0
Number of positions \| security	1	2
Fair Value	$ 446	$ 1,997
Unrealized Losses	$ 0	$ (1)
Government agency collateralized mortgage obligations \| Residential mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	25	5
Fair Value, Less than 12 Months	$ 537,594	$ 27,143
Unrealized Losses, Less than 12 Months	$ (4,324)	$ (51)
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	25	5
Fair Value	$ 537,594	$ 27,143
Unrealized Losses	$ (4,324)	$ (51)
Government agency collateralized mortgage obligations \| Commercial mortgage backed securities:
Available for Sale:
Number of positions, Less than 12 Months \| security	0	3
Fair Value, Less than 12 Months	$ 0	$ 14,190
Unrealized Losses, Less than 12 Months	$ 0	$ (21)
Number of positions, 12 Months or More \| security	13	0
Fair value, 12 Months or More	$ 115,433	$ 0
Unrealized Losses, 12 Months or More	$ (1,571)	$ 0
Number of positions \| security	13	3
Fair Value	$ 115,433	$ 14,190
Unrealized Losses	$ (1,571)	$ (21)

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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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