CONSOLIDATED STATEMENT OF REEDEMABLE CONVERTIBLE PREFERRED STOCK AND EQUITY - USD ($) $ in Thousands	Parent	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings (Deficit)	Noncontrolling Interest	Redeemable Convertible Preferred Stock	Total
Beginning balance at Dec. 31, 2014	$ 156,587	$ 18	$ 264,561	$ (41,058)	$ (66,934)	$ 32,333	$ 131,036	$ 188,920
Beginning balance (in shares) at Dec. 31, 2014		18,552					1,838
Changes in stockholders' equity
Net income	(966)				(966)	5,122		4,156
Issuance of common stock (in shares)		3,105
Issuance of common stock	41,801	$ 3	41,798					41,801
Exercise of common stock options (in shares)		164
Exercise of common stock options (in value)	2,752	$ 1	2,751					2,752
Other comprehensive income (loss)	(26,176)			(26,176)				(26,176)
Dividends paid on Series A redeemable convertible preferred stock	(13,747)				(13,747)			(13,747)
Dividends declared to noncontrolling interests						(4,200)		(4,200)
Ending balance at Dec. 31, 2015	160,251	$ 22	309,110	(67,234)	(81,647)	33,255	$ 131,036	193,506
Ending balance (in shares) at Dec. 31, 2015		21,821					1,838
Changes in stockholders' equity
Net income	45,012				45,012	4,503		49,515
Issuance of common stock (in shares)		3,105
Issuance of common stock	63,499	$ 3	63,496					63,499
Conversion of redeemable convertible preferred stock (in shares)		16,542					(1,838)
Conversion of redeemable convertible preferred stock (in Value)	131,036	$ 16	131,020				$ (131,036)	131,036
Conversion of convertible notes	362,489	$ 33	362,456					362,489
Conversion of convertible notes (in shares)		32,626
Other comprehensive income (loss)	(23,600)			(23,600)				(23,600)
Share-based compensation	14,494		14,494					14,494
Dividends paid on Series A redeemable convertible preferred stock	(17,316)				(17,316)		(13,700)	(17,316)
Dividends declared to noncontrolling interests						(4,800)		(4,800)
Ending balance at Dec. 31, 2016	735,865	$ 74	880,576	(90,834)	(53,951)	32,958		768,823
Ending balance (in shares) at Dec. 31, 2016		74,094
Changes in stockholders' equity
Net income	92,114				92,114	4,506		96,620
Other comprehensive income (loss)	9,143			9,143				9,143
Share-based compensation	15,054		15,054					15,054
Vesting of restricted common stock, net of shares withheld for employee taxes (in shares)		385
Vesting of restricted common stock, net of shares withheld for employee taxes (in value)	(903)		(903)					(903)
Dividends and dividend equivalents declared	(36,545)				(36,545)			(36,545)
Dividends paid on Series A redeemable convertible preferred stock							$ (17,300)
Dividends declared to noncontrolling interests						(4,800)		(4,800)
Ending balance at Dec. 31, 2017	$ 814,728	$ 74	$ 894,727	$ (81,691)	$ 1,618	$ 32,664		$ 847,392
Ending balance (in shares) at Dec. 31, 2017		74,479