Total Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Total Comprehensive Income [Abstract]
Net income	$ 10,607	$ 11,577	$ 28,049	$ 31,024
Unrealized security gains arising during the period	3,847	(1,122)	6,637	3,550
Reclassification adjustment for gains included in income	(458)	(272)	(954)	(3,401)
Net unrealized gains on securities	3,389	(1,394)	5,683	149
Unrealized loss on interest rate floors				(477)
Other comprehensive income (loss) before income taxes	3,389	(1,394)	5,683	(328)
Tax effect	(1,277)	531	(2,141)	124
Other comprehensive income (loss)	2,112	(863)	3,542	(204)
Total comprehensive income	$ 12,719	$ 10,714	$ 31,591	$ 30,820