Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financial assets:
Securities available for sale, at fair value	$ 1,359,129	$ 1,290,613
Trust preferred securities
Financial assets:
Securities available for sale, at fair value	8,604	9,986
Recurring
Financial assets:
Securities available for sale, at fair value	1,359,129	1,290,613
Derivative assets:	38,117	8,498
Mortgage loans held for sale in loans held for sale	448,797	318,272
Total financial assets	1,846,043	1,617,383
Financial liabilities:
Derivative instruments	37,256	10,000
Recurring \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value	8,604	9,986
Recurring \| Other available for sale securities
Financial assets:
Securities available for sale, at fair value	1,350,525	1,280,627
Recurring \| Level 1
Financial assets:
Securities available for sale, at fair value	0	0
Derivative assets:	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	0
Recurring \| Level 1 \| Other available for sale securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring \| Level 2
Financial assets:
Securities available for sale, at fair value	1,350,525	1,280,627
Derivative assets:	38,117	8,498
Mortgage loans held for sale in loans held for sale	448,797	318,272
Total financial assets	1,837,439	1,607,397
Financial liabilities:
Derivative instruments	37,256	10,000
Recurring \| Level 2 \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring \| Level 2 \| Other available for sale securities
Financial assets:
Securities available for sale, at fair value	1,350,525	1,280,627
Recurring \| Level 3
Financial assets:
Securities available for sale, at fair value	8,604	9,986
Derivative assets:	0	0
Mortgage loans held for sale in loans held for sale	0	0
Total financial assets	8,604	9,986
Financial liabilities:
Derivative instruments	0	0
Recurring \| Level 3 \| Trust preferred securities
Financial assets:
Securities available for sale, at fair value	8,604	9,986
Recurring \| Level 3 \| Other available for sale securities
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, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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