Fair Value Measurements (Summary Of Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 73,271,000	$ 67,760,000
Total gains or losses (realized /unrealized), included in earnings	4,470,000	(2,314,000)
Total gains or losses (realized /unrealized), included in other comprehensive income	133,000	391,000
Discount accretion	9,000	10,000
Purchase of private equity securities	4,879,000	4,825,000
Sales And Repayments Of Private Equity Securities	(20,000)	0
Capitalized interest/dividends	35,000	33,000
Sale Of Risk Participation Agreement	(148,000)	0
Ending balance	82,629,000	70,705,000
Total gains or losses included in earnings attributable to the change in unrealized gains or losses relating to assets still held at period end	5,050,000	(1,965,000)
State And Municipal Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	17,016,000	16,682,000
Total gains or losses (realized /unrealized), included in earnings	0	0
Total gains or losses (realized /unrealized), included in other comprehensive income	133,000	391,000
Discount accretion	9,000	10,000
Purchase of private equity securities	0	0
Sales And Repayments Of Private Equity Securities	0	0
Capitalized interest/dividends	0	0
Sale Of Risk Participation Agreement	0	0
Ending balance	17,158,000	17,083,000
Total gains or losses included in earnings attributable to the change in unrealized gains or losses relating to assets still held at period end	0	0
Private Equity Funds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	55,752,000	50,820,000
Total gains or losses (realized /unrealized), included in earnings	4,305,000	(2,878,000)
Total gains or losses (realized /unrealized), included in other comprehensive income	0	0
Discount accretion	0	0
Purchase of private equity securities	4,879,000	4,825,000
Sales And Repayments Of Private Equity Securities	(20,000)	0
Capitalized interest/dividends	35,000	33,000
Sale Of Risk Participation Agreement	0	0
Ending balance	64,951,000	52,800,000
Total gains or losses included in earnings attributable to the change in unrealized gains or losses relating to assets still held at period end	4,305,000	(2,878,000)
Derivative Level Three Unobservable Inputs [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	503,000	258,000
Total gains or losses (realized /unrealized), included in earnings	165,000	564,000
Total gains or losses (realized /unrealized), included in other comprehensive income	0	0
Discount accretion	0	0
Purchase of private equity securities	0	0
Sales And Repayments Of Private Equity Securities	0	0
Capitalized interest/dividends	0	0
Sale Of Risk Participation Agreement	(148,000)	0
Ending balance	520,000	822,000
Total gains or losses included in earnings attributable to the change in unrealized gains or losses relating to assets still held at period end	$ 745,000	$ 913,000