Securities - Contractual Maturity (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due within one year	$ 530,000
Due after one year through five years	2,064,000
Due after five years through ten years	18,368,000
Due after ten years	246,679,000
Amortized Cost	416,389,000	$ 0
Fair Value
Due within one year	529,000
Due after one year through five years	2,064,000
Due after five years through ten years	18,403,000
Due after ten years	246,291,000
Fair Value	415,552,000
Amortized Cost
Due within one year	8,523,000
Due after one year through five years	41,782,000
Due after five years through ten years	53,269,000
Due after ten years	77,798,000
Amortized Cost	2,400,956,000	1,301,973,000
Fair Value
Due within one year	8,579,000
Due after one year through five years	43,383,000
Due after five years through ten years	56,068,000
Due after ten years	79,610,000
Fair Value	2,386,052,000	1,343,457,000
Residential mortgage backed securities:
Amortized Cost
Amortized Cost	24,832,000
Fair Value
Fair Value	24,740,000
Residential mortgage backed securities: | Government agency mortgage backed securities
Amortized Cost
Without single maturity date, amortized cost	60,507,000
Amortized Cost	60,507,000
Fair Value
Without single maturity date, fair value	60,310,000
Fair Value	60,310,000
Amortized Cost
Without single maturity date, amortized cost	967,497,000
Amortized Cost	967,497,000	581,105,000
Fair Value
Without single maturity date, fair value	968,535,000
Fair Value	968,535,000	602,646,000
Residential mortgage backed securities: | Government agency collateralized mortgage obligations
Amortized Cost
Without single maturity date, amortized cost	24,832,000
Fair Value
Without single maturity date, fair value	24,740,000
Amortized Cost
Without single maturity date, amortized cost	1,008,514,000
Amortized Cost	1,008,514,000	218,373,000
Fair Value
Without single maturity date, fair value	988,600,000
Fair Value	988,600,000	220,268,000
Commercial mortgage backed securities: | Government agency mortgage backed securities
Amortized Cost
Without single maturity date, amortized cost	1,855,000
Amortized Cost	1,855,000
Fair Value
Without single maturity date, fair value	1,855,000
Fair Value	1,855,000
Amortized Cost
Without single maturity date, amortized cost	14,717,000
Amortized Cost	14,717,000	29,053,000
Fair Value
Without single maturity date, fair value	15,081,000
Fair Value	15,081,000	30,287,000
Commercial mortgage backed securities: | Government agency collateralized mortgage obligations
Amortized Cost
Without single maturity date, amortized cost	39,505,000
Amortized Cost	39,505,000
Fair Value
Without single maturity date, fair value	39,388,000
Fair Value	39,388,000
Amortized Cost
Without single maturity date, amortized cost	216,859,000
Amortized Cost	216,859,000	99,377,000
Fair Value
Without single maturity date, fair value	214,252,000
Fair Value	214,252,000	102,348,000
Other debt securities
Amortized Cost
Without single maturity date, amortized cost	22,049,000
Amortized Cost	22,049,000
Fair Value
Without single maturity date, fair value	21,972,000
Fair Value	21,970,000
Amortized Cost
Without single maturity date, amortized cost	11,997,000
Amortized Cost	36,515,000	62,771,000
Fair Value
Without single maturity date, fair value	11,944,000
Fair Value	$ 37,464,000	$ 65,607,000