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, 2010		$ 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)		257,000
Cancellation of restricted common stock		(525,000)				(525,000)
Cancellation of restricted common stock (in shares)		(23,000)
Stock options exercised		3,597,000				3,597,000
Stock options exercised (in shares)		192,000
Stock repurchased	(6,185,000)	(6,185,000)				(6,185,000)
Stock repurchased (in shares)	248,100	(248,000)
Share-based compensation, value	1,593,000	1,593,000				1,593,000
Tax benefit related to exercise of stock options		264,000				264,000
Net earnings	44,628,000		11,693,000		1,501,000	13,194,000	31,434,000
Distributions to noncontrolling interests, net of capital contributions					(1,385,000)	(1,385,000)	(30,455,000)
Sale of noncontrolling interest, value							(1,047,000)
Acquisitions and other transactions impacting noncontrolling interests					4,000	4,000	2,912,000
Gain on interest rate swap, net of income tax expense				377,000		377,000
Balance at Mar. 31, 2011		170,266,000	404,754,000	(138,000)	12,919,000	587,801,000	150,584,000
Balance (in shares) at Mar. 31, 2011		31,218,000
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
Issuance of restricted common stock (in shares)		255,000
Stock options exercised		2,521,000				2,521,000
Stock options exercised (in shares)	112,203,000	111,000
Stock repurchased	(1,560,000)	(2,823,000)				(2,823,000)
Stock repurchased (in shares)	61,149	(109,000)
Share-based compensation, value	1,792,000	1,792,000				1,792,000
Tax benefit related to exercise of stock options		198,000				198,000
Net earnings	54,939,000		14,776,000		6,062,000	20,838,000	34,101,000
Distributions to noncontrolling interests, net of capital contributions					(6,434,000)	(6,434,000)	(32,546,000)
Sale of noncontrolling interest, value		(1,587,000)			1,728,000	141,000
Acquisitions and other transactions impacting noncontrolling interests					2,223,000	2,223,000	2,467,000
Disposals and other transactions impacting noncontrolling interests		(369,000)				(369,000)	(176,000)
Balance at Mar. 31, 2012	$ 766,554,000	$ 172,919,000	$ 457,834,000	$ 0	$ 135,801,000	$ 766,554,000	$ 174,834,000
Balance (in shares) at Mar. 31, 2012		31,541,000