Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 23,361	$ 25,503
Available for sale securities:
Unrealized (losses) gains arising during the period	(4,425)	2,022
Reclassification adjustment for net gains realized in earnings (net of tax expense $3 and $59 for the three months ended March 31, 2013 and 2012, respectively)	(4)	(89)
Income tax benefit (expense) related to unrealized (losses) gains	1,770	(809)
Net change in unrealized gains	(2,659)	1,124
Held to maturity securities:
Accretion of unrealized losses related to factors other than credit to investment securities held to maturity (net of tax benefit of $12 and $28 for the three months ended March 31, 2013 and 2012, respectively)	17	41
Net change in unrealized losses related to factors other than credit	17	41
Other comprehensive (loss) income, net of tax	(2,642)	1,165
Comprehensive income	$ 20,719	$ 26,668