Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financial assets:
Securities available for sale, at fair value	$ 1,536,041	$ 1,343,457
Derivative instruments	30,352	3,866
Financial liabilities:
Derivative instruments	18,501	21,107
Trust preferred securities
Financial assets:
Securities available for sale, at fair value		9,012
Recurring
Financial assets:
Securities available for sale, at fair value		1,343,457
Derivative instruments	49,227	33,574
Mortgage loans held for sale in loans held for sale	502,002	417,771
Total financial assets	2,087,270	1,794,802
Financial liabilities:
Derivative instruments	18,985	21,107
Recurring \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value		9,012
Recurring \| Securities available for sale
Financial assets:
Securities available for sale, at fair value	1,536,041	1,334,445
Recurring \| Level 1
Financial assets:
Securities available for sale, at fair value		0
Derivative instruments	0	0
Mortgage loans held for sale in loans held for sale	0	0
Total financial assets	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring \| Level 1 \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value		0
Recurring \| Level 1 \| Securities available for sale
Financial assets:
Securities available for sale, at fair value	0	0
Recurring \| Level 2
Financial assets:
Securities available for sale, at fair value		1,334,445
Derivative instruments	49,227	33,574
Mortgage loans held for sale in loans held for sale	502,002	417,771
Total financial assets	2,087,270	1,785,790
Financial liabilities:
Derivative instruments	18,985	21,107
Recurring \| Level 2 \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value		0
Recurring \| Level 2 \| Securities available for sale
Financial assets:
Securities available for sale, at fair value	1,536,041	1,334,445
Recurring \| Level 3
Financial assets:
Securities available for sale, at fair value		9,012
Derivative instruments	0	0
Mortgage loans held for sale in loans held for sale	0	0
Total financial assets	0	9,012
Financial liabilities:
Derivative instruments	0	0
Recurring \| Level 3 \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value		9,012
Recurring \| Level 3 \| Securities available for sale
Financial assets:
Securities available for sale, at fair value	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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).

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Fair value portion of mortgage loans held-for-sale.

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