Investments (Aggregate Carrying And Approximate Market Values Of Held-To-Maturity Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	$ 60,827	$ 64,449
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	173	1,222
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	294	25
Securities held-to-maturity, Estimated Fair Value	60,706	65,646
Marketable Securities	812,891	628,985
Other Investments	28,810	14,147
Equity Securities
Schedule of Held-to-maturity Securities [Line Items]
Marketable Securities	10,313
US Government Agencies Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	56,827	60,449
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	173	1,222
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	294	25
Securities held-to-maturity, Estimated Fair Value	56,706	61,646
Trust preferred securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity, Amortized Cost	4,000	4,000
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Securities held-to-maturity, Estimated Fair Value	4,000	4,000
Securities
Schedule of Held-to-maturity Securities [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 18,497	$ 14,147