Fair Value of Financial Instruments - Hierarchy Table on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial assets
Investment securities available-for-sale, at fair value	$ 4,709,815	$ 3,931,115
Derivative assets	8,642
Financial liabilities
Derivative liabilities	5,819
U.S. Treasury
Financial assets
Investment securities available-for-sale, at fair value	79,342	32,533
Agency
Financial assets
Investment securities available-for-sale, at fair value	530,093	690,386
Corporate
Financial assets
Investment securities available-for-sale, at fair value	386,391	415,308
Municipal bonds
Financial assets
Investment securities available-for-sale, at fair value	1,255,866	1,446,019
Collateralized mortgage obligations
Financial assets
Investment securities available-for-sale, at fair value	662,231	513,366
Mortgage-backed securities
Financial assets
Investment securities available-for-sale, at fair value	1,795,892	833,503
Level 1
Financial assets
Investment securities available-for-sale, at fair value	0	0
Derivative assets	0	0
Financial liabilities
Derivative liabilities	0	0
Level 2
Financial assets
Investment securities available-for-sale, at fair value	4,709,815	3,931,115
Derivative assets	6,747	12,053
Financial liabilities
Derivative liabilities	5,819	12,066
Level 3
Financial assets
Investment securities available-for-sale, at fair value	0	0
Derivative assets	1,895	1,914
Financial liabilities
Derivative liabilities	0	0
Recurring
Financial assets
Investment securities available-for-sale, at fair value	4,709,815	3,931,115
Derivative assets	8,642	13,967
Financial liabilities
Derivative liabilities	5,819	12,066
Recurring | Interest rate swaps contracts
Financial assets
Derivative assets	6,747	12,053
Recurring | Equity warrants
Financial assets
Derivative assets	1,895	1,914
Recurring | U.S. Treasury
Financial assets
Investment securities available-for-sale, at fair value	79,342	32,533
Recurring | Agency
Financial assets
Investment securities available-for-sale, at fair value	530,093	690,386
Recurring | Corporate
Financial assets
Investment securities available-for-sale, at fair value	386,391	415,308
Recurring | Municipal bonds
Financial assets
Investment securities available-for-sale, at fair value	1,255,866	1,446,019
Recurring | Collateralized mortgage obligations
Financial assets
Investment securities available-for-sale, at fair value	662,231	513,366
Recurring | Mortgage-backed securities
Financial assets
Investment securities available-for-sale, at fair value	1,795,892	833,503
Recurring | Level 1
Financial assets
Investment securities available-for-sale, at fair value	0	0
Derivative assets	0	0
Financial liabilities
Derivative liabilities	0	0
Recurring | Level 1 | Interest rate swaps contracts
Financial assets
Derivative assets	0	0
Recurring | Level 1 | Equity warrants
Financial assets
Derivative assets	0	0
Recurring | Level 1 | U.S. Treasury
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 1 | Agency
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 1 | Corporate
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 1 | Municipal bonds
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 1 | Collateralized mortgage obligations
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 1 | Mortgage-backed securities
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 2
Financial assets
Investment securities available-for-sale, at fair value	4,709,815	3,931,115
Derivative assets	6,747	12,053
Financial liabilities
Derivative liabilities	5,819	12,066
Recurring | Level 2 | Interest rate swaps contracts
Financial assets
Derivative assets	6,747	12,053
Recurring | Level 2 | Equity warrants
Financial assets
Derivative assets	0	0
Recurring | Level 2 | U.S. Treasury
Financial assets
Investment securities available-for-sale, at fair value	79,342	32,533
Recurring | Level 2 | Agency
Financial assets
Investment securities available-for-sale, at fair value	530,093	690,386
Recurring | Level 2 | Corporate
Financial assets
Investment securities available-for-sale, at fair value	386,391	415,308
Recurring | Level 2 | Municipal bonds
Financial assets
Investment securities available-for-sale, at fair value	1,255,866	1,446,019
Recurring | Level 2 | Collateralized mortgage obligations
Financial assets
Investment securities available-for-sale, at fair value	662,231	513,366
Recurring | Level 2 | Mortgage-backed securities
Financial assets
Investment securities available-for-sale, at fair value	1,795,892	833,503
Recurring | Level 3
Financial assets
Investment securities available-for-sale, at fair value	0	0
Derivative assets	1,895	1,914
Financial liabilities
Derivative liabilities	0	0
Recurring | Level 3 | Interest rate swaps contracts
Financial assets
Derivative assets	0	0
Recurring | Level 3 | Equity warrants
Financial assets
Derivative assets	1,895	1,914
Recurring | Level 3 | U.S. Treasury
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 3 | Agency
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 3 | Corporate
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 3 | Municipal bonds
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 3 | Collateralized mortgage obligations
Financial assets
Investment securities available-for-sale, at fair value	0	0
Recurring | Level 3 | Mortgage-backed securities
Financial assets
Investment securities available-for-sale, at fair value	$ 0	$ 0