Consolidated Statements Of Changes In Equity (USD $)	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Non-Controlling Interests - Non-Redeemable [Member]	Total Equity (Permanent) [Member]	Non-controlling Interests - Redeemable (Temporary Equity) [Member]
Balance at Dec. 31, 2008		$ 172,192,000	$ 291,088,000	$ (2,851,000)	$ 2,877,000	$ 463,306,000	$ 63,202,000
Balance (in shares) at Dec. 31, 2008		31,342,000
Issuance of restricted common stock (in shares)		162,000
Cancellation of restricted common stock		(26,000)				(26,000)
Cancellation of restricted common stock (in shares)		(14,000)
Stock options exercised		201,000				201,000
Stock options exercised (in shares)	14,699	15,000
Stock repurchased	12,587,000	(12,587,000)				(12,587,000)
Stock repurchased (in shares)	830,700	(831,000)
Share-based compensation, value	4,068,000	4,068,000				4,068,000
Tax benefit related to exercise of stock options		2,000				2,000
Net earnings	181,350,000		52,148,000		4,065,000	56,213,000	125,137,000
Distributions to noncontrolling interests, net of capital contributions					(3,848,000)	(3,848,000)	(126,797,000)
Sale of noncontrolling interest, value		(121,000)				(121,000)	947,000
Acquisitions and other transactions impacting noncontrolling interests					2,161,000	2,161,000	60,874,000
Gain on interest rate swap, net of income tax expense				1,002,000		1,002,000
Balance at Dec. 31, 2009		163,729,000	343,236,000	(1,849,000)	5,255,000	510,371,000	123,363,000
Balance (in shares) at Dec. 31, 2009		30,674,000
Issuance of restricted common stock (in shares)		233,000
Cancellation of restricted common stock		(15,000)				(15,000)
Cancellation of restricted common stock (in shares)		(25,000)
Stock options exercised		2,583,000				2,583,000
Stock options exercised (in shares)	157,750	158,000
Share-based compensation, value	4,869,000	4,869,000				4,869,000
Tax benefit related to exercise of stock options		71,000				71,000
Net earnings	180,496,000		49,825,000		4,546,000	54,371,000	126,125,000
Distributions to noncontrolling interests, net of capital contributions					(4,844,000)	(4,844,000)	(127,193,000)
Purchase of noncontrolling interest, value		893,000			(137,000)	756,000	(1,046,000)
Sale of noncontrolling interest, value		(608,000)			434,000	(174,000)	614,000
Acquisitions and other transactions impacting noncontrolling interests					7,545,000	7,545,000	25,877,000
Gain on interest rate swap, net of income tax expense				1,334,000		1,334,000
Balance at Dec. 31, 2010	576,867,000	171,522,000	393,061,000	(515,000)	12,799,000	576,867,000	147,740,000
Balance (in shares) at Dec. 31, 2010		31,040,000
Issuance of restricted common stock (in shares)		277,000
Cancellation of restricted common stock		(9,000)				(9,000)
Cancellation of restricted common stock (in shares)		(1,000)
Stock options exercised		6,872,000				6,872,000
Stock options exercised (in shares)	374,350	374,000
Stock repurchased	8,584,000	(10,007,000)				(10,007,000)
Stock repurchased (in shares)	344,100	(406,000)
Share-based compensation, value	6,178,000	6,178,000				6,178,000
Tax benefit related to exercise of stock options		649,000				649,000
Net earnings	190,114,000		49,997,000		10,181,000	60,178,000	129,936,000
Distributions to noncontrolling interests, net of capital contributions					(9,502,000)	(9,502,000)	(129,979,000)
Purchase of noncontrolling interest, value		195,000			(817,000)	(622,000)	(788,000)
Sale of noncontrolling interest, value		(1,702,000)			439,000	(1,263,000)	1,771,000
Acquisitions and other transactions impacting noncontrolling interests					122,276,000	122,276,000	21,390,000
Disposals and other transactions impacting noncontrolling interests		(511,000)			(3,154,000)	(3,665,000)	566,000
Gain on interest rate swap, net of income tax expense				515,000		515,000
Balance at Dec. 31, 2011	$ 748,467,000	$ 173,187,000	$ 443,058,000	$ 0	$ 132,222,000	$ 748,467,000	$ 170,636,000
Balance (in shares) at Dec. 31, 2011		31,284,000