Employee Benefit Plans (Fair Value Of Pension Plan Assets By Asset Category) (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
U.S. government obligations		$ 816,514	$ 1,035,406
Government-sponsored enterprise obligations		43,962	43,108
State and municipal obligations		1,197,419	1,767,109
Agency mortgage-backed securities		3,901,346	4,308,427
Non-agency mortgage-backed securities		1,157,898	1,211,607
Asset-backed securities		2,107,485	3,397,801
Pension Plans [Member]
U.S. government obligations		14,041	9,960
Government-sponsored enterprise obligations	[1]	1,039	1,022
State and municipal obligations		3,740	6,840
Agency mortgage-backed securities	[2]	2,230	2,871
Non-agency mortgage-backed securities		2,271	2,527
Asset-backed securities		5,687	6,768
Corporate bonds	[3]	48,534	35,234
Mutual funds	[4]	4,443	4,395
Common stocks	[4]	5,809	15,868
International developed markets	[4]	1,809	2,604
Emerging markets	[4]	239	307
Total		89,842	88,396
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
U.S. government obligations		816,514	1,035,406
Government-sponsored enterprise obligations		0	0
State and municipal obligations		0	0
Agency mortgage-backed securities		0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Pension Plans [Member]
U.S. government obligations		14,041	9,960
Government-sponsored enterprise obligations	[1]	0	0
State and municipal obligations		0	0
Agency mortgage-backed securities	[2]	0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Corporate bonds	[3]	0	0
Mutual funds	[4]	4,443	4,395
Common stocks	[4]	5,809	15,868
International developed markets	[4]	1,809	2,604
Emerging markets	[4]	239	307
Total		26,341	33,134
Significant Other Observable Inputs (Level 2) [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations		43,962	43,108
State and municipal obligations		1,196,472	1,765,268
Agency mortgage-backed securities		3,901,346	4,308,427
Non-agency mortgage-backed securities		1,157,898	1,211,607
Asset-backed securities		2,107,485	3,397,801
Significant Other Observable Inputs (Level 2) [Member] | Pension Plans [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations	[1]	1,039	1,022
State and municipal obligations		3,740	6,840
Agency mortgage-backed securities	[2]	2,230	2,871
Non-agency mortgage-backed securities		2,271	2,527
Asset-backed securities		5,687	6,768
Corporate bonds	[3]	48,534	35,234
Mutual funds	[4]	0	0
Common stocks	[4]	0	0
International developed markets	[4]	0	0
Emerging markets	[4]	0	0
Total		63,501	55,262
Significant Unobservable Inputs (Level 3) [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations		0	0
State and municipal obligations		947	1,841
Agency mortgage-backed securities		0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Significant Unobservable Inputs (Level 3) [Member] | Pension Plans [Member]
U.S. government obligations		0	0
Government-sponsored enterprise obligations	[1]	0	0
State and municipal obligations		0	0
Agency mortgage-backed securities	[2]	0	0
Non-agency mortgage-backed securities		0	0
Asset-backed securities		0	0
Corporate bonds	[3]	0	0
Mutual funds	[4]	0	0
Common stocks	[4]	0	0
International developed markets	[4]	0	0
Emerging markets	[4]	0	0
Total		$ 0	$ 0

[1] This category represents bonds (excluding mortgage-backed securities) issued by agencies such as the Government National Mortgage Association, the Federal Home Loan Mortgage Corp and the Federal National Mortgage Association.

[2] This category represents mortgage-backed securities issued by the agencies mentioned in (a).

[3] This category represents investment grade bonds issued in the U.S., primarily by domestic issuers, representing diverse industries.

[4] This category represents investments in individual common stocks and equity funds. These holdings are diversified, largely across the technology services, financial services, electronic technology, healthcare technology, and retail trade industries.