Accumulated Other Comprehensive Income - Reclassification from AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other noninterest income									$ 2,496	$ 2,487	$ 2,420
Tax (expense) benefit	(1,927)	(3,625)	(3,188)	(2,389)	(2,354)	(2,705)	(2,863)	(2,990)	(11,129)	(10,912)	(10,542)
Net income	5,150	7,899	7,181	6,744	5,583	6,624	6,914	6,810	26,974	25,931	26,833
Net unrealized gain on available-for-sale securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other noninterest income									0	17	(6)
Tax (expense) benefit									0	(7)	2
Net income									$ 0	$ 10	$ (4)