Investments (Aggregate Carrying And Approximate Market Values Of Available-For-Sale Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 776,226	$ 732,853
Gross Unrealized Gains	24,435	3,153
Gross Unrealized Losses	1,731	14,210
Estimated Fair Value	798,930	721,796
U.S Treasuries and U.S. Government Agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,279	5,713
Gross Unrealized Gains	25	20
Gross Unrealized Losses	0	0
Estimated Fair Value	1,304	5,733
Obligations Of States And Political Subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	110,714	128,089
Gross Unrealized Gains	5,232	1,033
Gross Unrealized Losses	7	1,052
Estimated Fair Value	115,939	128,070
U.S. Government Agencies Mortgage-backed Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	613,884	561,799
Gross Unrealized Gains	17,863	1,950
Gross Unrealized Losses	985	12,991
Estimated Fair Value	630,762	550,758
Private Label
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,132	11,948
Gross Unrealized Gains	718	95
Gross Unrealized Losses	0	0
Estimated Fair Value	11,850	12,043
Trust Preferred Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,779	4,774
Gross Unrealized Gains	35	25
Gross Unrealized Losses	595	0
Estimated Fair Value	4,219	4,799
Corporate Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	31,948	16,795
Gross Unrealized Gains	562	30
Gross Unrealized Losses	144	167
Estimated Fair Value	32,366	16,658
Debt Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	773,736	729,118
Gross Unrealized Gains	24,435	3,153
Gross Unrealized Losses	1,731	14,210
Estimated Fair Value	796,440	718,061
Certificates of Deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,490	3,735
Estimated Fair Value	$ 2,490	$ 3,735