Securities Securities - Amortized Cost, Allowance for Credit Losses and Estimated Fair Value of Securities Held to Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	$ 3,711,841	$ 2,639,241
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	34,823	13,048
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	144,907	184,424
Debt Securities, Held-to-maturity, Fair Value	3,601,757	2,467,865
Securities, held-to-maturity, allowance for credit loss	(262)	(158)
Securities held to maturity, net of allowance for credit losses of $262 at March 31, 2023 and $158 at December 31, 2022	3,711,579	2,639,083
Residential Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,273,079	526,122
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	3,859	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	56,728	65,322
Debt Securities, Held-to-maturity, Fair Value	1,220,210	460,800
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $262 at March 31, 2023 and $158 at December 31, 2022	1,273,079	526,122
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	2,437,262	2,111,619
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	30,964	13,048
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	88,103	119,033
Debt Securities, Held-to-maturity, Fair Value	2,380,123	2,005,634
Securities, held-to-maturity, allowance for credit loss	(262)	(158)
Securities held to maturity, net of allowance for credit losses of $262 at March 31, 2023 and $158 at December 31, 2022	2,437,000	2,111,461
Other Investments [Member]
Schedule of Investments [Line Items]
Held to Maturity, Amortized Cost	1,500	1,500
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	76	69
Debt Securities, Held-to-maturity, Fair Value	1,424	1,431
Securities, held-to-maturity, allowance for credit loss	0	0
Securities held to maturity, net of allowance for credit losses of $262 at March 31, 2023 and $158 at December 31, 2022	$ 1,500	$ 1,500