Consolidated Statements of Changes in Equity and Comprehensive Income (USD $) In Thousands, unless otherwise specified		Total	Common Stock [Member]	Premium on Common Stock [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Noncontrolling Interest in Subsidiaries [Member]
Balance at Dec. 31, 2009		$ 544,564	$ 37,245	$ 254,503	$ (183)	$ (19,469)	$ 271,505	$ 963
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		66,652					66,652
Other Comprehensive Income (Loss), Net of Tax	[1]	(2,343)				(2,343)
Common Stock Issued or Granted Under Stock Plans		2,665	96	2,771	4		(206)
Cash Dividends Declared - Common Stock		(40,478)					(40,478)
Deconsolidation of Joint Ventures (See Note 1)		(963)						(963)
Balance at Dec. 31, 2010		570,097	37,341	257,274	(179)	(21,812)	297,473	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		89,291					89,291
Other Comprehensive Income (Loss), Net of Tax	[1]	(6,626)				(6,626)
Common Stock Issued or Granted Under Stock Plans		16,327	424	16,029	(14)		(112)
Cash Dividends Declared - Common Stock		(44,975)					(44,975)
Balance at Dec. 31, 2011		624,114	37,765	273,303	(193)	(28,438)	341,677	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		91,608					91,608
Other Comprehensive Income (Loss), Net of Tax	[1]	(2,667)				(2,667)
Common Stock Issued or Granted Under Stock Plans		74,101	1,802	72,504	11		(216)
Cash Dividends Declared - Common Stock		(50,942)					(50,942)
Additional Statement Information [Abstract]
Combined statutory tax rate		41.00%
Balance at Dec. 31, 2012		$ 736,214	$ 39,567	$ 345,807	$ (182)	$ (31,105)	$ 382,127	$ 0

[1] Determined using a combined statutory tax rate of 41%.