Consolidated Statement Of Equity - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]	Total
Balance at Dec. 31, 2016	$ 90,155	$ 797,513	$ 1,032,844	$ (71,113)	$ 669	$ 1,850,068
Net income			49,072			49,072
Other comprehensive loss, net of income tax benefit of $31					58	58
Dividends			(33,945)			(33,945)
Sale of stock (11,898 shares)	6	354				360
Repurchase of stock (66,036 shares)				(2,053)		(2,053)
Equity compensation plan (156,359 shares)	79	(79)
Exercise of stock options (86,511 shares)	43	1,493				1,536
Stock-based compensation		1,345	10			1,355
Cumulative effect of change in accounting principle - windfall tax benefit			982			982
Other		(206)				(206)
Balance at Mar. 31, 2017	$ 90,283	$ 800,420	$ 1,048,963	$ (73,166)	$ 727	$ 1,867,227