Fair Value of Assets and Liabilities - Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial Assets
Debt securities, available-for-sale	$ 4,741,738	$ 5,307,307
Recurring Measurements
Financial Assets
Loans held for sale, at fair value	29,027	12,314
Total assets measured at fair value on a recurring basis	4,778,725	5,327,740
Total financial liabilities		188
U.S. government and federal agency
Financial Assets
Debt securities, available-for-sale	444,145	444,727
U.S. government and federal agency | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	444,145	444,727
U.S. government sponsored enterprises
Financial Assets
Debt securities, available-for-sale	289,831	287,364
U.S. government sponsored enterprises | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	289,831	287,364
State and local governments
Financial Assets
Debt securities, available-for-sale	96,713	132,993
State and local governments | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	96,713	132,993
Corporate bonds
Financial Assets
Debt securities, available-for-sale	25,904	26,109
Corporate bonds | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	25,904	26,109
Residential mortgage-backed securities
Financial Assets
Debt securities, available-for-sale	2,810,894	3,267,341
Residential mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	2,810,894	3,267,341
Commercial mortgage-backed securities
Financial Assets
Debt securities, available-for-sale	1,074,251	1,148,773
Commercial mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	1,074,251	1,148,773
Interest rate caps | Recurring Measurements
Financial Assets
Derivative assets	6,840	7,757
Interest rate locks | Recurring Measurements
Financial Assets
Derivative assets	789	362
TBA hedge | Recurring Measurements
Financial Assets
Derivative assets	331
TBA hedge		188
Level 1 | Recurring Measurements
Financial Assets
Loans held for sale, at fair value	0	0
Total assets measured at fair value on a recurring basis	0	0
Total financial liabilities		0
Level 1 | U.S. government and federal agency | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 | U.S. government sponsored enterprises | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 | State and local governments | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 | Corporate bonds | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 | Residential mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 | Commercial mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 | Interest rate caps | Recurring Measurements
Financial Assets
Derivative assets	0	0
Level 1 | Interest rate locks | Recurring Measurements
Financial Assets
Derivative assets	0	0
Level 1 | TBA hedge | Recurring Measurements
Financial Assets
Derivative assets	0
TBA hedge		0
Level 2 | Recurring Measurements
Financial Assets
Loans held for sale, at fair value	29,027	12,314
Total assets measured at fair value on a recurring basis	4,778,725	5,327,740
Total financial liabilities		188
Level 2 | U.S. government and federal agency | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	444,145	444,727
Level 2 | U.S. government sponsored enterprises | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	289,831	287,364
Level 2 | State and local governments | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	96,713	132,993
Level 2 | Corporate bonds | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	25,904	26,109
Level 2 | Residential mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	2,810,894	3,267,341
Level 2 | Commercial mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	1,074,251	1,148,773
Level 2 | Interest rate caps | Recurring Measurements
Financial Assets
Derivative assets	6,840	7,757
Level 2 | Interest rate locks | Recurring Measurements
Financial Assets
Derivative assets	789	362
Level 2 | TBA hedge | Recurring Measurements
Financial Assets
Derivative assets	331
TBA hedge		188
Level 3 | Recurring Measurements
Financial Assets
Loans held for sale, at fair value	0	0
Total assets measured at fair value on a recurring basis	0	0
Total financial liabilities		0
Level 3 | U.S. government and federal agency | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 | U.S. government sponsored enterprises | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 | State and local governments | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 | Corporate bonds | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 | Residential mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 | Commercial mortgage-backed securities | Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 | Interest rate caps | Recurring Measurements
Financial Assets
Derivative assets	0	0
Level 3 | Interest rate locks | Recurring Measurements
Financial Assets
Derivative assets	0	0
Level 3 | TBA hedge | Recurring Measurements
Financial Assets
Derivative assets	$ 0
TBA hedge		$ 0