Fair Value of Assets and Liabilities - Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial Assets
Debt securities, available-for-sale	$ 5,337,814	$ 2,575,252
Carrying Amount
Financial Liabilities
Total financial liabilities	2,156,389	1,788,967
Recurring measurements
Financial Assets
Loans held for sale, at fair value	166,572	69,194
Total assets measured at fair value on a recurring basis	5,513,192	2,646,298
Financial Liabilities
Total financial liabilities	2,056	236
Interest Rate Swaps
Financial Liabilities
TBA hedge
Interest Rate Swaps \| Recurring measurements
Financial Liabilities
TBA hedge	2,056	236
Interest Rate Cap \| Recurring measurements
Financial Assets
Interest rate caps	201
Interest Rate Lock Commitments \| Recurring measurements
Financial Assets
Interest rate caps	8,605	1,852
U.S. government and federal agency \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	38,588	20,044
U.S. government sponsored enterprises \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	9,781	43,677
State and local governments \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	1,416,683	702,398
Corporate bonds \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	349,098	157,602
Residential mortgage-backed securities \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	2,289,090	738,724
Commercial mortgage-backed securities \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	1,234,574	912,807
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
Financial Liabilities
Total financial liabilities	0	0
Level 1 \| Interest Rate Swaps \| Recurring measurements
Financial Liabilities
TBA hedge	0	0
Level 1 \| Interest Rate Cap \| Recurring measurements
Financial Assets
Interest rate caps	0
Level 1 \| Interest Rate Lock Commitments \| Recurring measurements
Financial Assets
Interest rate caps	0	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 2 \| Recurring measurements
Financial Assets
Loans held for sale, at fair value	166,572	69,194
Total assets measured at fair value on a recurring basis	5,513,192	2,646,298
Financial Liabilities
Total financial liabilities	2,056	236
Level 2 \| Interest Rate Swaps \| Recurring measurements
Financial Liabilities
TBA hedge	2,056	236
Level 2 \| Interest Rate Cap \| Recurring measurements
Financial Assets
Interest rate caps	201
Level 2 \| Interest Rate Lock Commitments \| Recurring measurements
Financial Assets
Interest rate caps	8,605	1,852
Level 2 \| U.S. government and federal agency \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	38,588	20,044
Level 2 \| U.S. government sponsored enterprises \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	9,781	43,677
Level 2 \| State and local governments \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	1,416,683	702,398
Level 2 \| Corporate bonds \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	349,098	157,602
Level 2 \| Residential mortgage-backed securities \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	2,289,090	738,724
Level 2 \| Commercial mortgage-backed securities \| Recurring measurements
Financial Assets
Debt securities, available-for-sale	1,234,574	912,807
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
Financial Liabilities
Total financial liabilities	0	0
Level 3 \| Interest Rate Swaps \| Recurring measurements
Financial Liabilities
TBA hedge	0	0
Level 3 \| Interest Rate Cap \| Recurring measurements
Financial Assets
Interest rate caps	0
Level 3 \| Interest Rate Lock Commitments \| Recurring measurements
Financial Assets
Interest rate caps	0	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

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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