Investment Securities - Amortized Cost and Fair Value of Available for Sale Securities and Held to Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 6,954
Due after one through five years	5,097
Due after five through ten years	120,460
Due after ten years	1,464,460
Total debt securities with a single maturity date	1,596,971
Total Investment Securities	2,268,655
Fair Value
Due in one year or less	6,965
Due after one through five years	5,309
Due after five through ten years	126,816
Due after ten years	1,537,856
Total debt securities with a single maturity date	1,676,946
Total Investment Securities	2,344,551	$ 1,919,119
Amortized Cost
Due in one year or less	6,971
Due after one through five years	30,272
Due after five through ten years	177,203
Due after ten years	1,215,812
Total debt securities with a single maturity date	1,430,258
Amortized Cost	2,180,047	1,227,668
Fair Value
Due in one year or less	6,995
Due after one through five years	31,946
Due after five through ten years	180,129
Due after ten years	1,231,568
Total debt securities with a single maturity date	1,450,638
Total Investment Securities	2,202,503	1,280,293
U.S. Government-sponsored mortgage-backed securities
Amortized Cost
Without single maturity date	671,684
Fair Value
Without single maturity date	667,605
Total Investment Securities	667,605	612,091
Amortized Cost
Without single maturity date	749,789
Amortized Cost	749,789	460,843
Fair Value
Without single maturity date	751,865
Total Investment Securities	$ 751,865	$ 478,395