Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Non-Controlling Interest
Beginning Balance at Dec. 31, 2012	$ 1,277,366	$ 77	$ 815,936	$ 509,604		$ (159,690)	$ 111,439
Beginning Balance (in shares) at Dec. 31, 2012		76,549,000
Issuance of common stock related to acquisition of interest in joint venture	$ 17,246		17,246
Shares issued on vesting of restricted stock (in shares)		368,000
Shares issued on exercise of stock options and warrants (in shares)	131,073	131,000
Shares issued on exercise of stock options and warrants	$ 353		353
Purchase of minority interest in consolidated joint venture	1,500		1,500
Tax benefit of stock option exercises	1,196		1,196
Tax effect on formation of joint venture	(5,168)		(5,168)
Compensation expense in connection with restricted stock and stock options	20,018		20,018
Shares repurchased on the open market	(436,419)					(436,419)
Cost of shares repurchased on vesting of restricted stock and exercise of stock options	(3,707)					(3,707)
Non-controlling interest of acquired companies	(2,765)						(2,765)
Consideration received from non-controlling interest	20,780			(253)			21,033
Amounts due from non-controlling interest holders	(10,565)						(10,565)
Net income (loss)	117,292			104,989			12,303
Net cost of hedge on convertible notes	3,038		3,038
Foreign currency translation gain (loss)	16,486				$ 16,486
Distributions to joint ventures	(8,516)						(8,516)
Equity portion of convertible notes	52,362		52,362
Ending Balance at Dec. 31, 2013	1,060,497	$ 77	906,481	614,340	16,486	(599,816)	122,929
Ending Balance (in shares) at Dec. 31, 2013		77,048,000
Shares issued on vesting of restricted stock (in shares)		883,000
Shares issued on vesting of restricted stock	$ 1	$ 1
Shares issued on exercise of stock options and warrants (in shares)	1,172,000	1,332,000
Shares issued on exercise of stock options and warrants	$ 10,088	$ 1	10,087
Purchase of minority interest in consolidated joint venture	(525)		(525)
Tax benefit of stock option exercises	10,703		10,703
Tax effect on formation of joint venture	(4,316)		(4,316)
Compensation expense in connection with restricted stock and stock options	18,492		18,492
Shares repurchased on the open market	(193,434)					(193,434)
Cost of shares repurchased on vesting of restricted stock and exercise of stock options	(19,179)					(19,179)
Non-controlling interest of acquired companies	11,526						11,526
Payments from non-controlling interest holders	549						549
Change in redemption value of redeemable non-controlling interest holders	(3,051)			(3,051)
Net income (loss)	118,822			103,723			15,099
Foreign currency translation gain (loss)	(40,672)				(40,672)
Distributions to joint ventures	(18,064)			(1,193)			(16,871)
Ending Balance at Dec. 31, 2014	951,437	$ 79	940,922	713,819	(24,186)	(812,429)	133,232
Ending Balance (in shares) at Dec. 31, 2014		79,263,000
Issuance of common stock related to acquisition of interest in joint venture (in shares)		465,000
Issuance of common stock related to acquisition of interest in joint venture	15,703		15,703
Shares issued on vesting of restricted stock (in shares)		806,000
Shares issued on vesting of restricted stock	$ 1	$ 1
Shares issued on exercise of stock options and warrants (in shares)	75,000	75,000
Shares issued on exercise of stock options and warrants	$ 321		321
Purchase of minority interest in consolidated joint venture	(2,885)		3,863				(6,748)
Tax benefit of stock option exercises	2,006		2,006
Compensation expense in connection with restricted stock and stock options	11,449		11,449
Shares repurchased on the open market	(12,391)					(12,391)
Cost of shares repurchased on vesting of restricted stock and exercise of stock options	(12,359)					(12,359)
Non-controlling interest of acquired companies	(9,168)						(9,168)
Payments from non-controlling interest holders	3,523						3,523
Change in redemption value of redeemable non-controlling interest holders	(5,015)			(5,015)
Change in fair value of available for sale securities	(703)				(703)
Net income (loss)	(188,930)			(189,303)			373
Foreign currency translation gain (loss)	(36,004)				(36,004)
Distributions to joint ventures	(22,080)			(4,740)			(17,340)
Ending Balance at Dec. 31, 2015	$ 694,905	$ 80	$ 974,264	$ 514,761	$ (60,893)	$ (837,179)	$ 103,872
Ending Balance (in shares) at Dec. 31, 2015		80,609,000