CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balances at Dec. 31, 2012	$ 24,905	$ 191,689	$ 255,606	$ 11,312	$ 483,512
Net income			34,809		34,809
Other comprehensive income (loss), net of tax				(14,204)	(14,204)
Common stock dividends			(11,590)		(11,590)
Stock compensation expense		1,307			1,307
Common stock issued pursuant to:
Stock option plan	11	128			139
Employee stock purchase plan	20	336			356
Restricted stock	49	(496)			(447)
Balances at Sep. 30, 2013	24,985	192,964	278,825	(2,892)	493,882
Balances at Dec. 31, 2013	24,990	193,445	283,898	(2,970)	499,363
Net income			29,052		29,052
Other comprehensive income (loss), net of tax				6,602	6,602
Common stock dividends			(14,154)		(14,154)
Stock compensation expense		1,318			1,318
Common stock issued pursuant to:
Stock option plan	14	176			190
Employee stock purchase plan	18	365			383
Restricted stock	55	(405)			(350)
Balances at Sep. 30, 2014	$ 25,077	$ 194,899	$ 298,796	$ 3,632	$ 522,404