Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (17,605)	$ (323)
Other comprehensive income before reclassifications	10,488	(15,416)
Amounts reclassified from accumulated other comprehensive income	(358)	(1,866)
Other comprehensive income (loss), net of tax	10,130	(17,282)	3,646
Ending balance	(7,475)	(17,605)	(323)
Unrealized gains (losses) on available for sale securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(14,476)	3,650
Other comprehensive income before reclassifications	12,060	(16,447)
Amounts reclassified from accumulated other comprehensive income	(601)	(1,679)
Other comprehensive income (loss), net of tax	11,459	(18,126)
Ending balance	(3,017)	(14,476)
Interest rate swaps [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	0
Other comprehensive income before reclassifications	(331)
Amounts reclassified from accumulated other comprehensive income	7
Other comprehensive income (loss), net of tax	(324)
Ending balance	(324)
Defined benefit plan items [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(3,129)	(3,973)
Other comprehensive income before reclassifications	(1,241)	1,031
Amounts reclassified from accumulated other comprehensive income	236	(187)
Other comprehensive income (loss), net of tax	(1,005)	844
Ending balance	$ (4,134)	$ (3,129)