Fair Value Measurements - General Disclosures (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	$ 3,997,244	$ 2,261,187
Equity securities	13,012	5,530
Loans held for sale, at fair value	20,225	42,813
U.S. Treasury securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	185,453	27,837
Obligations of U.S. government corporations and agencies
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	38,997	69,519
Obligations of states and political subdivisions
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	296,012	304,711
Commercial mortgage-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	603,297	418,616
Residential mortgage-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	2,102,608	1,368,315
Asset-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	468,807
Corporate debt securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	302,070	72,189
Recurring basis
Financial assets and financial liabilities measured at fair value
Equity securities	13,012	5,530
Loans held for sale, at fair value	20,225	42,813
Recurring basis \| Derivative assets
Financial assets and financial liabilities measured at fair value
Derivative asset	21,869	33,918
Recurring basis \| Derivative liabilities
Financial assets and financial liabilities measured at fair value
Derivative liability	24,501	38,403
Recurring basis \| U.S. Treasury securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	185,453	27,837
Recurring basis \| Obligations of U.S. government corporations and agencies
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	38,997	69,519
Recurring basis \| Obligations of states and political subdivisions
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	296,012	304,711
Recurring basis \| Commercial mortgage-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	603,297	418,616
Recurring basis \| Residential mortgage-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	2,102,608	1,368,315
Recurring basis \| Asset-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	468,807
Recurring basis \| Corporate debt securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	302,070	72,189
Recurring basis \| Level 2
Financial assets and financial liabilities measured at fair value
Equity securities	13,012	5,530
Loans held for sale, at fair value	20,225	42,813
Recurring basis \| Level 2 \| Derivative assets
Financial assets and financial liabilities measured at fair value
Derivative asset	21,869	33,918
Recurring basis \| Level 2 \| Derivative liabilities
Financial assets and financial liabilities measured at fair value
Derivative liability	24,501	38,403
Recurring basis \| Level 2 \| U.S. Treasury securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	185,453	27,837
Recurring basis \| Level 2 \| Obligations of U.S. government corporations and agencies
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	38,997	69,519
Recurring basis \| Level 2 \| Obligations of states and political subdivisions
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	296,012	304,711
Recurring basis \| Level 2 \| Commercial mortgage-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	603,297	418,616
Recurring basis \| Level 2 \| Residential mortgage-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	2,102,608	1,368,315
Recurring basis \| Level 2 \| Asset-backed securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	468,807
Recurring basis \| Level 2 \| Corporate debt securities
Financial assets and financial liabilities measured at fair value
Debt securities available for sale	$ 302,070	$ 72,189

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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Amount, after valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security.

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