Securities - Available-for-Sale Securities Held by Company (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,063,790	$ 1,599,894
Gross Unrealized Gains	13,626	30,773
Gross Unrealized Losses	32,903	3,474
Fair Value	2,044,513	1,627,193
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	160,291
Gross Unrealized Gains	85
Gross Unrealized Losses	2,542
Fair Value	157,834
Obligations of U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	843,218	599,652
Gross Unrealized Gains	4,527	9,820
Gross Unrealized Losses	15,372	1,992
Fair Value	832,373	607,480
Obligations of U.S. states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	102,177	126,642
Gross Unrealized Gains	2,092	3,144
Gross Unrealized Losses	100	40
Fair Value	104,169	129,746
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	76,502	179,538
Gross Unrealized Gains	1,187	3,216
Gross Unrealized Losses	532	646
Fair Value	77,157	182,108
U.S. Government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	879,102	691,562
Gross Unrealized Gains	5,735	14,593
Gross Unrealized Losses	14,281	675
Fair Value	870,556	705,480
U.S. corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,500	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	76	121
Fair Value	$ 2,424	$ 2,379

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Section 50
-Paragraph 2
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
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