Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Condensed Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 23,277	$ 17,785	$ 48,780	$ 31,252
Available for sale securities:
Unrealized (losses) gains arising during the period	(6,050)	24,835	(4,029)	25,649
Reclassification adjustment for net gains realized in earnings (net of tax expense $412 and $2,271 for the three months ended June 30, 2012 and 2011, respectively, and net of tax expense of $471 and $2,271 for the six months ended June 30, 2012 and 2011, respectively)	(618)	(3,407)	(707)	(3,407)
Income tax benefit (expense) related to unrealized gains	2,420	(9,934)	1,612	(10,259)
Net change in unrealized gains	(4,248)	11,494	(3,124)	11,983
Held to maturity securities:
Unrealized losses related to factors other than credit (net of tax benefit of $35 and $30 for the three and six months ended June 30, 2011, respectively)		(53)		(45)
Reclassification adjustment for impairments realized in net income (net of tax benefit of $10 and $20 for the three and six months ended June 30, 2011, respectively)		15		30
Accretion of unrealized losses related to factors other than credit to investment securities held to maturity (net of tax benefit of $25 and $10 for the three months ended June 30, 2012 and 2011, respectively, and net of tax benefit of $53 and $27 for the six months ended June 30, 2012 and 2011, respectively)	38	15	79	41
Net change in unrealized losses related to factors other than credit	38	(23)	79	26
Other comprehensive (loss) income, net of tax	(4,210)	11,471	(3,045)	12,009
Comprehensive income	$ 19,067	$ 29,256	$ 45,735	$ 43,261