CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	Total
Balance at Dec. 31, 2014	$ 48,671	$ 1,025,941	$ 332,511	$ (41,618)		$ 1,365,505
Net income			45,292			45,292
Other comprehensive income (loss)				(547)		(547)
Tax effect of share-based compensation		(186)				(186)
Share-based compensation expense		9,477				9,477
Issuance of common stock, net	402	284				686
Balance at Dec. 31, 2015	49,073	1,035,516	377,803	(42,165)		1,420,227
Net income			95,822			95,822
Other comprehensive income (loss)				(3,248)		(3,248)
Tax effect of share-based compensation		(457)				(457)
Share-based compensation expense		13,423				13,423
Issuance of common stock, net	138	676				814
Convertible note proceeds allocated to conversion option, net		26,442				26,442
Balance at Dec. 31, 2016	49,211	1,075,600	473,625	(45,413)		1,553,023
Net income			148,382		$ 6,162	154,544
Other comprehensive income (loss)				2,695		2,695
Share-based compensation expense		20,877				20,877
Issuance of common stock, net	570	(12,272)				(11,702)
Contributions from noncontrolling interests					2,842	2,842
Distributions to noncontrolling interests					(17,499)	(17,499)
Balance at Dec. 31, 2017	$ 49,781	$ 1,084,205	$ 622,007	$ (42,718)	$ (8,495)	$ 1,704,780