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, 2012	$ 714,897	$ 805	$ 97,457	$ 758,617	$ (4,156)	$ (137,826)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	86,310	0	0	86,785	(475)	0
Purchases of common stock	(20,060)	0	0	0	0	(20,060)
Dividends on common stock	(14,560)	0	0	(14,560)	0	0
Equity compensation activity, including excess tax benefits	1,123	0	(3,732)	0	0	4,855
Non-cash equity compensation expense	4,809	0	4,809	0	0	0
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)