Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Condensed Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 25,153	$ 21,862	$ 73,933	$ 53,114
Available for sale securities:
Unrealized gains (losses) arising during the period	1,863	12,065	(2,167)	37,714
Reclassification adjustment for net gains realized in earnings (net of tax expense $8 and $725 for the three months ended September 30, 2012 and 2011, respectively, and net of tax expense of $480 and $2,996 for the nine months ended September 30, 2012 and 2011, respectively)	(13)	(1,088)	(719)	(4,495)
Income tax (expense) benefit related to unrealized gains (losses)	(745)	(4,826)	867	(15,086)
Net change in unrealized gains	1,105	6,151	(2,019)	18,133
Held to maturity securities:
Unrealized losses related to factors other than credit (net of tax benefit of $30 for the nine months ended September 30, 2011)				(45)
Reclassification adjustment for impairments realized in net income (net of tax benefit of $20 for the nine months ended September 30, 2011)				30
Accretion of unrealized losses related to factors other than credit to investment securities held to maturity (net of tax benefit of $23 and $17 for the three months ended September 30, 2012 and 2011, respectively, and net of tax benefit of $76 and $44 for the nine months ended September 30, 2012 and 2011, respectively)	35	25	114	67
Net change in unrealized losses related to factors other than credit	35	25	114	52
Other comprehensive income (loss), net of tax	1,140	6,176	(1,905)	18,185
Comprehensive income	$ 26,293	$ 28,038	$ 72,028	$ 71,299