Fair Value - Assets and Liabilities Recorded at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets
Total available-for-sale securities, Fair value,	$ 8,062,384	$ 8,428,032
Collateralized Loan Obligations
Assets
Total available-for-sale securities, Fair value,	220,884	105,247
Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	8,062,384	8,428,032
Other assets	23,031	58,307
Liabilities
Other liabilities	(19,207)	(6,768)
Total
Net Assets (Liabilities)	8,066,208	8,479,571
Fair Value, Measurements, Recurring | Level 1
Assets
Other assets	6,617	7,382
Total
Net Assets (Liabilities)	6,617	7,382
Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	8,062,384	8,428,032
Other assets	16,414	50,925
Liabilities
Other liabilities	(13,413)	(1,238)
Total
Net Assets (Liabilities)	8,065,385	8,477,719
Fair Value, Measurements, Recurring | Level 3
Liabilities
Other liabilities	(5,794)	(5,530)
Total
Net Assets (Liabilities)	(5,794)	(5,530)
U.S. Treasury and government agency debt securities
Assets
Total available-for-sale securities, Fair value,	199,544	192,563
U.S. Treasury and government agency debt securities | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	199,544	192,563
U.S. Treasury and government agency debt securities | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	199,544	192,563
Residential - Government agency
Assets
Total available-for-sale securities, Fair value,	122,965	137,264
Residential - Government agency | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	122,965	137,264
Residential - Government agency | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	122,965	137,264
Residential - Government-sponsored enterprises
Assets
Total available-for-sale securities, Fair value,	1,362,345	1,491,100
Residential - Government-sponsored enterprises | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	1,362,345	1,491,100
Residential - Government-sponsored enterprises | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	1,362,345	1,491,100
Commercial - Government agency
Assets
Total available-for-sale securities, Fair value,	333,089	387,663
Commercial - Government agency | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	333,089	387,663
Commercial - Government agency | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	333,089	387,663
Commercial - Government-sponsored enterprises
Assets
Total available-for-sale securities, Fair value,	1,249,834	1,369,443
Commercial - Government-sponsored enterprises | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	1,249,834	1,369,443
Commercial - Government-sponsored enterprises | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	1,249,834	1,369,443
Government agency
Assets
Total available-for-sale securities, Fair value,	2,009,781	2,079,523
Government agency | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	2,009,781	2,079,523
Government agency | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	2,009,781	2,079,523
Government-sponsored enterprises
Assets
Total available-for-sale securities, Fair value,	2,509,707	2,621,044
Government-sponsored enterprises | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	2,509,707	2,621,044
Government-sponsored enterprises | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	2,509,707	2,621,044
Collateralized Loan Obligations | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	220,884	105,247
Collateralized Loan Obligations | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	220,884	105,247
Debt securities issued by states and political subdivisions
Assets
Total available-for-sale securities, Fair value,	54,235	44,185
Debt securities issued by states and political subdivisions | Fair Value, Measurements, Recurring
Assets
Total available-for-sale securities, Fair value,	54,235	44,185
Debt securities issued by states and political subdivisions | Fair Value, Measurements, Recurring | Level 2
Assets
Total available-for-sale securities, Fair value,	$ 54,235	$ 44,185