Other Comprehensive Income (Schedule of Calculation of Other Comprehensive Income) (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Amortization of accumulated pension loss	$ 821	$ 566	$ 1,901	$ 1,700
Net unrealized gains (losses)			48,422	35,274
Net unrealized gains			2,835	12,469
Other comprehensive income	32,781	19,407	52,436	48,797
Available for Sale Debt Securities for Which a Portion of OTTI Has Been Recorded in Earnings [Member]
Unrealized holding gains (losses) subsequent to initial OTTI recognition	(1,091)	8,145	4,572	20,112
Income tax (expense) benefit	415	(3,096)	(1,737)	(7,643)
Net unrealized gains (losses)	(676)	5,049	2,835	12,469
Other Available for Sale Investment Securities [Member]
Unrealized holding gains (losses) subsequent to initial OTTI recognition	53,143	23,353	78,278	59,426
Reclassification adjustment for gains included in net income		(764)	(177)	(2,534)
Net unrealized gains on securities	53,143	22,589	78,101	56,892
Income tax (expense) benefit	(20,195)	(8,582)	(29,679)	(21,618)
Net unrealized gains	32,948	14,007	48,422	35,274
Prepaid Pension Cost [Member]
Amortization of accumulated pension loss	821	566	1,901	1,700
Income tax (expense) benefit	(312)	(215)	(722)	(646)
Pension loss amortization	$ 509	$ 351	$ 1,179	$ 1,054