Consolidated Statement of Stockholders' Equity - 6 months ended Jun. 30, 2017 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in-Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance, shares at Dec. 31, 2016		25,663
Beginning balance at Dec. 31, 2016	$ 930,200	$ 257	$ 290,899	$ 1,053,301	$ (146,944)	$ (267,313)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	73,072	0	0	73,072	0	0
Other comprehensive income (loss), net of tax	10,676	0	0	0	10,676	0
Stock Issued During Period, Value, Treasury Stock Reissued	(41,015)	$ 0	0	0	0	(41,015)
Stock Issued During Period, Shares, Employee Stock Purchase Plans		(98)
Stock Issued During Period, Value, Employee Stock Purchase Plan	(1,545)	$ (1)	(13,927)	0	0	12,383
Stock-based compensation	10,438	0	10,438	0	0	0
Cash dividends	(10,178)	$ 0	0	(10,178)	0	0
Ending balance, shares at Jun. 30, 2017		25,565
Ending balance at Jun. 30, 2017	$ 971,648	$ 256	287,410	$ 1,116,195	$ (136,268)	$ (295,945)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation