Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2013	33,301
Balance at Dec. 31, 2013	$ 333	$ 85,077	$ 273,727	$ 359,137
Net income			29,834	29,834
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	118
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 1	1,213		1,214
Tax benefits from share-based payment arrangement exercises		159		159
Share-based payment arrangement compensation expense		921		921
Dividends on common stock			(3,339)	(3,339)
Balance (in shares) at Dec. 31, 2014	33,419
Balance at Dec. 31, 2014	$ 334	87,370	300,222	387,926
Tax benefits from share-based payment arrangement exercises		159		159
Net income			35,745	35,745
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	282
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 3	3,487		3,490
Tax benefits from share-based payment arrangement exercises		373		373
Share-based payment arrangement compensation expense		1,404		1,404
Dividends on common stock			(3,342)	(3,342)
Balance (in shares) at Dec. 31, 2015	32,760
Balance at Dec. 31, 2015	$ 328	76,468	332,625	409,421
Repurchase and retirement of common stock (in shares)	(941)
Repurchase and retirement of common stock	$ (9)	(16,166)		(16,175)
Tax benefits from share-based payment arrangement exercises		373		373
Net income			33,464	33,464
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	331
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 3	4,413		4,416
Tax benefits from share-based payment arrangement exercises		46		46
Share-based payment arrangement compensation expense		883		883
Dividends on common stock			(3,252)	(3,252)
Balance (in shares) at Dec. 31, 2016	32,635
Balance at Dec. 31, 2016	$ 326	74,175	$ 362,837	437,338
Repurchase and retirement of common stock (in shares)	(456)
Repurchase and retirement of common stock	$ (5)	(7,508)		(7,513)
Tax benefits from share-based payment arrangement exercises		46		46
Employee taxes paid in exchange for shares withheld		$ (127)		$ (127)