Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Restricted Stock Units Restricted Stock Units	Additional Paid-in Capital	Exchangeable Shares of Subsidiary	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance at Dec. 31, 2015		$ 405	$ 84,969	$ 697,607	$ 1,958	$ 109,860	$ (28,405)	$ (583,038)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued		9		44,789
Restricted stock units recognized, net of forfeitures			45,880
Restricted stock units delivered			(44,942)
Tax (expense) from the delivery of restricted stock units				(7,668)
Exchangeable shares of subsidiary delivered					0
Dividends						(61,609)
Tax benefit from payment of restricted stock unit dividends						2,785
Net income allocated to common stockholders						60,762
Currency translation adjustment, net of tax							(3,993)
Repurchased								(28,186)
Ending Balance at Dec. 31, 2016	$ 291,183	414	85,907	734,728	1,958	111,798	(32,398)	(611,224)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued		10		39,815
Restricted stock units recognized, net of forfeitures			20,263
Restricted stock units delivered			(40,224)
Tax (expense) from the delivery of restricted stock units				847
Exchangeable shares of subsidiary delivered					0
Dividends						(30,794)
Tax benefit from payment of restricted stock unit dividends						0
Net income allocated to common stockholders	5,499					5,499
Currency translation adjustment, net of tax	6,731						6,731
Repurchased								(12,733)
Ending Balance at Jun. 30, 2017	$ 280,597	$ 424	$ 65,946	$ 775,390	$ 1,958	$ 86,503	$ (25,667)	$ (623,957)