Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
BALANCE at Dec. 31, 2013	$ 772,519	$ 805	$ 98,534	$ 830,842	$ (4,631)	$ (153,031)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	93,906	0	0	98,650	(4,744)	0
Purchases of common stock	(30,587)	0	0	0	0	(30,587)
Dividends on common stock	(14,407)	0	0	(14,407)	0	0
Equity compensation activity, including excess tax benefits	6,359	0	(2,801)	0	0	9,160
Non-cash equity compensation expense	6,070	0	6,070	0	0	0
BALANCE at Dec. 31, 2014	833,860	805	101,803	915,085	(9,375)	(174,458)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	120,026	0	0	123,714	(3,688)	0
Purchases of common stock	(6,438)	0	0	0	0	(6,438)
Dividends on common stock	(15,833)	0	0	(15,833)	0	0
Equity compensation activity, including excess tax benefits	(322)	0	(3,430)	0	0	3,108
Non-cash equity compensation expense	4,361	0	4,361	0	0	0
BALANCE at Dec. 31, 2015	935,654	805	102,734	1,022,966	(13,063)	(177,788)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	75,275	0	0	79,129	(3,854)	0
Dividends on common stock	(17,299)	0	0	(17,299)	0	0
Equity compensation activity, including excess tax benefits	(1,224)	0	(4,080)	0	0	2,856
Non-cash equity compensation expense	2,381	0	2,381	0	0	0
BALANCE at Dec. 31, 2016	$ 994,787	$ 805	$ 101,035	$ 1,084,796	$ (16,917)	$ (174,932)