Comprehensive Income (Schedule of Comprehensive Income) (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income as reported	$ 18,872	$ 5,204	$ 33,283	$ 18,176
Net unrealized holding gain from available for sale securities arising during the period	4,988	4,739	13,768	11,897
Reclassification adjustment of net gain from sale of available for sale securities included in income	0	0	0	(38)
Net unrealized gain from securities, net of reclassification adjustment	4,988	4,739	13,768	11,859
Cash flow hedging instruments: Reclassification adjustment of net gain included in income	0	(216)	(143)	(943)
Net change in cash flow hedging instruments	0	(216)	(143)	(943)
Pension plan liability adjustment: Net unrealized gain from unfunded defined benefit plan liability arising during the period	0	0	(260)	23
Pension plan liability adjustment: Less: amortization of unrecognized net actuarial loss included in net periodic pension cost	14	7	41	21
Pension plan liability adjustment, net	14	7	(219)	44
Total comprehensive income	23,874	9,734	46,689	29,136
Net unrealized holding gain from available for sale securities arising during the period, tax	0	(2,611)	0	(6,553)
Reclassification adjustment of net gain from sale of available for sale securities included in income, tax	0	0	0	20
Cash flow hedging instruments: Reclassification adjustment of net gain included in income, tax	0	119	0	520
Net unrealized gain loss from unfunded defined benefit plan liability arising during period, tax	0	4	0	12
Amortization of unrecognized net actuarial loss included in net periodic pension cost, tax	$ 0	$ 0	$ 0	$ 11