Condensed Consolidated Statements of Comprehensive Income (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 5,807	$ 3,504
Available for sale securities
Unrealized gain (loss) arising during period	974	(1,037)
Change in unrealized losses for which a portion of other than temporary impairment has been recognized in earnings	33	129
Reclassification adjustment for other than temporary impairment included in earnings	0	177
Reclassification adjustments for (gains) losses included in earnings	7	(692)
Unrealized gains (losses) recognized in other comprehensive income on available for sale securities	1,014	(1,423)
Income tax expense	0	0
Unrealized gains (losses) recognized in other comprehensive income on available for sale securities, net of tax	1,014	(1,423)
Derivative instruments
Unrealized loss arising during period	(3)	(51)
Reclassification adjustment for expense recognized in earnings	94	185
Reclassification adjustment for accretion on settled derivatives	0	145
Unrealized gains recognized in other comprehensive income on derivative instruments	91	279
Income tax expense	0	0
Unrealized gains recognized in other comprehensive income on derivative instruments, net of tax	91	279
Net current-period other comprehensive income (loss)	1,105	(1,144)
Comprehensive income	$ 6,912	$ 2,360