Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Contingent convertible preferred stock	Restricted stock units Restricted stock units	Additional paid-in capital	Exchangeable shares of subsidiary	Retained earnings	Accumulated other comprehensive income	Treasury stock	Parent
Beginning Balance at Dec. 31, 2014		$ 389	$ 14,446	$ 90,107	$ 596,463	$ 1,958	$ 141,290	$ (17,969)	$ (571,136)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		16			94,554
Contingent convertible preferred stock canceled or converted			(14,446)		(14,446)
Restricted stock units recognized, net of forfeitures				47,071
Restricted stock units delivered				(52,209)
Tax benefit (expense)					(7,856)		1,912
Exchangeable shares of subsidiary delivered						0
Dividends							(58,940)
Net income (loss) allocated to common stockholders	$ 25,598						25,598
Currency translation adjustment, net of tax	(10,436)							(10,436)
Repurchased									(11,902)
Ending Balance at Dec. 31, 2015		405	0	84,969	697,607	1,958	109,860	(28,405)	(583,038)	$ 283,356
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		9			44,789
Contingent convertible preferred stock canceled or converted			0		0
Restricted stock units recognized, net of forfeitures				45,880
Restricted stock units delivered				(44,942)
Tax benefit (expense)					(7,668)		2,785
Exchangeable shares of subsidiary delivered						0
Dividends							(61,609)
Net income (loss) allocated to common stockholders	60,762						60,762
Currency translation adjustment, net of tax	(3,993)							(3,993)
Repurchased									(28,186)
Ending Balance at Dec. 31, 2016		414	0	85,907	734,728	1,958	111,798	(32,398)	(611,224)	291,183
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		24			65,231
Contingent convertible preferred stock canceled or converted			0		0
Restricted stock units recognized, net of forfeitures				40,597
Restricted stock units delivered				(45,992)
Tax benefit (expense)					847		0
Exchangeable shares of subsidiary delivered						0
Dividends							(47,552)
Net income (loss) allocated to common stockholders	(26,651)						(26,651)
Currency translation adjustment, net of tax	$ 10,176							10,176
Repurchased									(79,561)
Ending Balance at Dec. 31, 2017		$ 438	$ 0	$ 80,512	$ 800,806	$ 1,958	$ 37,595	$ (22,222)	$ (690,785)	$ 208,302