Consolidated Statement Of Equity (USD $) In Thousands	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 31, 2010	$ 69,223	$ 664,369	$ 452,470	$ (12,307)	$ 499	$ 572	$ 1,174,826
Net income			109,064			13	109,077
Unrealized holding loss on investments, net of income tax of $149					(277)		(277)
Reclassification adjustment for gain reported in net income, net of income tax of $84					(156)		(156)
Dividends paid			(64,266)				(64,266)
Dividends declared			(22,863)				(22,863)
Sale of stock (445,004 shares)	215	8,861		325			9,401
Repurchase of stock (44,165 shares)				(1,001)			(1,001)
Equity compensation plan (14,176 shares)	7	(7)
Exercise of stock options (375,023 shares)	188	5,647					5,835
Stock-based compensation		2,852	(47)				2,805
Employee stock plan tax benefits		(573)					(573)
Balance at Sep. 30, 2011	$ 69,633	$ 681,149	$ 474,358	$ (12,983)	$ 66	$ 585	$ 1,212,808