Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2013	$ 801,581	$ 285,535	$ 532,087	$ (16,041)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	84,401	0	84,401	0
Other comprehensive loss, net of tax	13,507	0	0	13,507
Common stock transactions:
Common shares purchased and retired	9,739	(9,739)	0	0
Common shares issued	35,674	35,674	0	0
Non-vested common shares issued	0	0	0	0
Non-vested common shares forfeited or canceled	0	0	0	0
Stock options exercised, net of shares tendered in payment of option price and income tax withholding amounts	6,299	6,299	0	0
Tax benefit of stock-based compensation	2,193	2,193	0	0
Stock-based compensation expense	3,634	3,634	0	0
Cash dividends declared:
Common (per share)	(28,626)	0	(28,626)	0
Ending Balance at Dec. 31, 2014	908,924	323,596	587,862	(2,534)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	86,795	0	86,795	0
Other comprehensive loss, net of tax	2,940	0	0	2,940
Common stock transactions:
Common shares purchased and retired	(20,647)	(20,647)	0	0
Common shares issued	0	0	0	0
Non-vested common shares issued	0	0	0	0
Non-vested common shares forfeited or canceled	0	0	0	0
Stock options exercised, net of shares tendered in payment of option price and income tax withholding amounts	3,369	3,369	0	0
Tax benefit of stock-based compensation	1,443	1,443	0	0
Stock-based compensation expense	3,959	3,959	0	0
Cash dividends declared:
Common (per share)	(36,290)	0	(36,290)	0
Ending Balance at Dec. 31, 2015	950,493	311,720	638,367	406
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	95,636	0	95,636	0
Other comprehensive loss, net of tax	(8,534)	0	0	(8,534)
Common stock transactions:
Common shares purchased and retired	(26,854)	(26,854)	0	0
Common shares issued	0	0	0	0
Non-vested common shares issued	0	0	0	0
Non-vested common shares forfeited or canceled	0	0	0	0
Stock options exercised, net of shares tendered in payment of option price and income tax withholding amounts	4,683	4,683	0	0
Tax benefit of stock-based compensation	2,146	2,146	0	0
Stock-based compensation expense	4,376	4,376	0	0
Cash dividends declared:
Common (per share)	(39,353)	0	(39,353)	0
Ending Balance at Dec. 31, 2016	$ 982,593	$ 296,071	$ 694,650	$ (8,128)