Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Shares Purchased to Fund Options Exercised [Member] Treasury Stock [Member]	Shares Purchased to Fund Options Exercised [Member]	Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member] Treasury Stock [Member]	Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2013					$ 315	$ 201,902	$ (22,053)	$ 263,743	$ (11,375)	$ 432,532
Net income								44,239		44,239
Award of common shares released from Employee Benefit Trust						2,075				2,075
Vesting of restricted stock unit awards						(2,775)	3,205	(430)
Exercise of stock options						143	499	(77)		565
Stock-based compensation expense						4,246				4,246
Stock-based income tax benefit						846				846
Purchase of treasury shares	$ (17,644)	$ (17,644)	$ (1,228)	$ (1,228)
Dividends on common stock								(17,852)		(17,852)
Other comprehensive income									8,468	8,468
Balance at Dec. 31, 2014					315	206,437	(37,221)	289,623	(2,907)	456,247
Net income								46,209		46,209
Award of common shares released from Employee Benefit Trust						2,092				2,092
Vesting of restricted stock unit awards						(3,076)	3,580	(504)
Exercise of stock options						(51)	378	(182)		145
Stock-based compensation expense						4,676				4,676
Stock-based income tax benefit						574				574
Purchase of treasury shares	(14,351)	(14,351)	(1,254)	(1,254)
Dividends on common stock								(18,616)		(18,616)
Other comprehensive income									(2,655)	(2,655)
Balance at Dec. 31, 2015					315	210,652	(48,868)	316,530	(5,562)	473,067
Net income								64,916		64,916
Award of common shares released from Employee Benefit Trust						2,057				2,057
Vesting of restricted stock unit awards						(4,049)	4,446	(397)
Exercise of stock options						(30)	526	(168)		328
Stock-based compensation expense						5,120				5,120
Stock-based income tax benefit						712				712
Purchase of treasury shares	$ (8,031)	$ (8,031)	$ (1,827)	$ (1,827)
Dividends on common stock								(19,689)		(19,689)
Other comprehensive income									(2,800)	(2,800)
Balance at Dec. 31, 2016					$ 315	$ 214,462	$ (53,754)	$ 361,192	$ (8,362)	$ 513,853