Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Non-Controlling Interest
Beginning Balance at Dec. 31, 2008	$ 644,089	$ 59	$ 533,234	$ 120,358	$ (3,880)	$ (5,682)
Beginning Balance (in shares) at Dec. 31, 2008		59,077,000
Shares issued on exercise of stock options (in shares)	828,059	828,000
Shares issued on exercise of stock options	3,230	1	3,229
Shares issued on vesting of restricted stock		268,000
Shares issued for earn-out on acquisition (in shares)		1,297,000
Shares issued for earn-out on acquisition	15,676	1	15,675
Issuance of new stock (in shares)		10,700,000
Issuance of new stock	152,798	11	152,787
Issuance of common stock related to joint venture (in shares)		589,000
Issuance of common stock related to joint venture	7,999	1	7,998
Shares repurchased on vesting of restricted stock and exercise of stock options	(724)					(724)
Shares repurchased on open market	(1,455)					(1,455)
Tax benefit of stock option exercises	3,600		3,600
Amortization expense in connection with restricted stock	8,925		8,925
Amortization expense in connection with convertible notes	56		56
Comprehensive income	75,879			75,111	(152)		920
Non-controlling interest of acquired companies	59,699						59,699
Ending Balance at Dec. 31, 2009	969,772	73	725,504	195,469	(4,032)	(7,861)	60,619
Ending Balance (in shares) at Dec. 31, 2009		72,759,000
Shares issued on exercise of stock options (in shares)	499,700	499,000
Shares issued on exercise of stock options	2,083		2,083
Shares issued on vesting of restricted stock		75,000
Shares issued for earn-out on acquisition (in shares)		597,000
Shares issued for earn-out on acquisition	12,472	1	12,471
Shares repurchased on vesting of restricted stock and exercise of stock options	(2,970)					(2,970)
Tax benefit of stock option exercises	1,301		1,301
Compensation expense in connection with restricted stock and stock options	11,444		11,444
Comprehensive income	114,512			98,847	4,032		11,633
Distribution to Joint Ventures	(3,078)						(3,078)
Non-controlling interest of acquired companies	33,378						33,378
Ending Balance at Dec. 31, 2010	1,138,914	74	752,803	294,316		(10,831)	102,552
Ending Balance (in shares) at Dec. 31, 2010		73,930,000
Shares issued on exercise of stock options and warrants (in shares)		968,000
Shares issued on exercise of stock options and warrants	3,312	1	3,311
Shares issued on exercise of stock options (in shares)	911,527
Shares issued on vesting of restricted stock		351,000
Shares issued for earn-out on acquisition (in shares)		144,000
Shares issued for earn-out on acquisition	2,776		2,776
Shares repurchased on vesting of restricted stock and exercise of stock options	(3,185)					(3,185)
Shares repurchased on open market	(19,138)					(19,138)
Tax benefit of stock option exercises	4,940		4,940
Compensation expense in connection with restricted stock and stock options	11,742		11,742
Equity portion of convertible notes	35,996		35,996
Net cost of hedge on convertible notes	(9,374)		(9,374)
Comprehensive income	140,758			126,105	(483)		15,136
Distribution to Joint Ventures	(11,895)						(11,895)
Distribution of capital proceeds	(18,000)						(18,000)
Non-controlling interest of acquired companies	16,730						16,730
Ending Balance at Dec. 31, 2011	$ 1,293,576	$ 75	$ 802,194	$ 420,421	$ (483)	$ (33,154)	$ 104,523
Ending Balance (in shares) at Dec. 31, 2011		75,393,000