Other Comprehensive Income (Loss) (Component Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Other Comprehensive Income (Loss) [Abstract]
Changes in pension plan assets and benefit obligations, Before-tax amount	$ (31,603)	$ (32,237)	$ (24,503)
Changes in pension plan assets and benefit obligations, Tax expense (benefit)	(11,061)	(11,283)	(8,576)
Changes in pension plan assets and benefit obligations, Net-of-tax amount	(20,542)	(20,954)	(15,927)
Unrealized gains on available-for-sale securities, Before-tax amount	16,108	19,498	13,462
Unrealized gains on available-for-sale securities, Tax expense (benefit)	5,637	6,825	4,712
Unrealized gains on available-for-sale securities, Net-of-tax amount	10,471	12,673	8,750
Unrealized net holding loss on cash flow hedge, Before-tax amount	(673)	(846)	(1,430)
Unrealized net holding loss on cash flow hedge, Tax expense (benefit)	(236)	(296)	(501)
Unrealized net holding loss on cash flow hedge, Net-of-tax amount	(437)	(550)	(929)
Total accumulated other comprehensive income (loss), Before-tax amount	(16,168)	(13,585)	(12,471)
Total accumulated other comprehensive income (loss), Tax expense (benefit)	(5,660)	(4,754)	(4,365)
Total accumulated other comprehensive income (loss), Net-of-tax amount	$ (10,508)	$ (8,831)	$ (8,106)