Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 43,214	$ 32,694	$ 23,818
Unrealized gains (losses) on securities:
Unrealized gains (losses) on available-for-sale securities arising during the period	17,437	(12,853)	2,522
Income tax effect	(6,103)	4,499	(883)
Reclassification adjustment for available-for-sale-security gains included in net income	(3,191)	(1,274)	(9,017)
Income tax effect	1,117	446	3,156
Unrealized holding gains on available-for-sale securities transferred from the held-to-maturity category into the available-for-sale category	0	0	8,509
Income tax effect	0	0	(2,978)
Net unrealized gains (losses) on securities	9,260	(9,182)	1,309
Unrealized losses on cash flow hedges arising during the period	(1,945)	0	0
Income tax effect	681	0	0
Net unrealized losses on cash flow hedges	(1,264)	0	0
Other comprehensive income (loss), net of income tax effect	7,996	(9,182)	1,309
Comprehensive income	$ 51,210	$ 23,512	$ 25,127