Available-For-Sale And Held-To-Maturity Securities (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011	Dec. 31, 2011
Carrying value of securities pledged as collateral	$ 712,000,000			$ 712,000,000			$ 634,800,000
Available-for-sale securities, Estimated fair value	1,476,681,000			1,476,681,000			1,214,141,000
Available-for-sale Securities, Amortized cost	1,446,097,000			1,446,097,000			1,204,205,000
Credit-related other-than-temporary impairment				300,000
Gross unrealized losses related to all other securities	2,804,000	[1]		2,804,000	[1]		8,114,000	[1]
Unrealized gains on available-for-sale securities, net of tax	8,356,000		(3,393,000)	12,714,000		3,245,000
Realized gains resulted from sale of available-for-sale securities	1,000,000			3,100,000
Proceeds from sale of available-for-sale securities	92,400,000			186,500,000
Available-for-sale securities related to individual securities, number of positions	22			22
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	22			22
Available-For-Sale Securities [Member]
Available-for-sale securities, Estimated fair value	139,900,000			139,900,000
Available-for-sale securities, percentage of investment portfolio	9.50%			9.50%
Available-for-sale Securities, Amortized cost	142,700,000			142,700,000
Gross unrealized losses related to all other securities	$ 2,800,000			$ 2,800,000

[1] Unrealized gains/(losses) related to available-for-sale securities are reported in accumulated other comprehensive loss.