Fair Value Measurements - Assets and liabilities recorded at fair value on recurring basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	$ 1,786,659	$ 1,151,083
U.S. treasuries
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	24,854
U. S. agency securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	353,706	181,921
Residential mortgage backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	1,203,136	825,001
Loans held for sale	53,413	88,205
Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	123,164	108,113
Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	81,601	35,850
Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for sale	53,413	88,205
Assets measured at fair value on a nonrecurring basis	1,846,321	1,247,716
Derivative liability	73	118
Total liabilities measured at fair value on a recurring basis	5,110	4,208
Recurring \| Interest rate swap derivatives
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability	0	516
Recurring \| Interest rate caps
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	4,882	3,413
Derivative liability	5,037	3,574
Recurring \| U.S. treasuries
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	24,854
Recurring \| U. S. agency securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	353,706	181,921
Recurring \| Residential mortgage backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	1,203,136	825,001
Recurring \| Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	123,164	108,113
Recurring \| Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	81,601	35,850
Recurring \| Mortgage banking derivatives \| Derivative Financial Instruments, Assets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	1,565	5,213
Recurring \| Fair Value, Inputs, Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for sale	0	0
Assets measured at fair value on a nonrecurring basis	0	0
Derivative liability	0	0
Total liabilities measured at fair value on a recurring basis	0	0
Recurring \| Fair Value, Inputs, Level 1 \| Interest rate swap derivatives
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability	0	0
Recurring \| Fair Value, Inputs, Level 1 \| Interest rate caps
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	0	0
Derivative liability	0	0
Recurring \| Fair Value, Inputs, Level 1 \| U.S. treasuries
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	0
Recurring \| Fair Value, Inputs, Level 1 \| U. S. agency securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	0	0
Recurring \| Fair Value, Inputs, Level 1 \| Residential mortgage backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	0	0
Recurring \| Fair Value, Inputs, Level 1 \| Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	0	0
Recurring \| Fair Value, Inputs, Level 1 \| Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	0	0
Recurring \| Fair Value, Inputs, Level 1 \| Mortgage banking derivatives \| Derivative Financial Instruments, Assets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	0	0
Recurring \| Fair Value, Inputs, Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for sale	53,413	88,205
Assets measured at fair value on a nonrecurring basis	1,843,256	1,241,003
Derivative liability	73	118
Total liabilities measured at fair value on a recurring basis	5,110	4,208
Recurring \| Fair Value, Inputs, Level 2 \| Interest rate swap derivatives
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability	0	516
Recurring \| Fair Value, Inputs, Level 2 \| Interest rate caps
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	4,882	3,413
Derivative liability	5,037	3,574
Recurring \| Fair Value, Inputs, Level 2 \| U.S. treasuries
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	24,854
Recurring \| Fair Value, Inputs, Level 2 \| U. S. agency securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	353,706	181,921
Recurring \| Fair Value, Inputs, Level 2 \| Residential mortgage backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	1,203,136	825,001
Recurring \| Fair Value, Inputs, Level 2 \| Municipal bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	123,164	108,113
Recurring \| Fair Value, Inputs, Level 2 \| Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	80,101	34,350
Recurring \| Fair Value, Inputs, Level 2 \| Mortgage banking derivatives \| Derivative Financial Instruments, Assets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	0	0
Recurring \| Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets measured at fair value on a nonrecurring basis	3,065	6,713
Total liabilities measured at fair value on a recurring basis	0	0
Recurring \| Fair Value, Inputs, Level 3 \| Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment securities	1,500	1,500
Recurring \| Fair Value, Inputs, Level 3 \| Mortgage banking derivatives \| Derivative Financial Instruments, Assets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset	$ 1,565	$ 5,213

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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Fair value of financial and nonfinancial obligations.

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