Statements of Consolidated Total Equity - USD ($) $ in Thousands	Total	Preferred shares at par value	Common shares at par value Class A common shares at par value	Common shares at par value Class B common shares at par value	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income/(loss)	Class B common shares held by a subsidiary	Non-controlling interests
Beginning balance at Dec. 31, 2015	$ 658,425	$ 0	$ 1,015	$ 181	$ 975,419	$ 21,734	$ (340,104)	$ (181)	$ 361
Increase (Decrease) in Stockholders' Equity
Share-based compensation	6,272				6,272
Exercised stock options and vested share awards	17		5		12
Repurchase of shares	(1,992)		(2)		(2,245)	255
Dividend to non-controlling interest	(223)								(223)
Comprehensive loss:
Net earnings (losses) attributable to common shares	36,433					36,324			109
Other comprehensive loss	(12,100)						(12,235)		135
Ending balance at Dec. 31, 2016	686,832	0	1,018	181	979,458	58,313	(352,339)	(181)	382
Increase (Decrease) in Stockholders' Equity
Share-based compensation	5,809				5,809
Exercised stock options and vested share awards	305		6		299
Dividend to non-controlling interest	(146)								(146)
Comprehensive loss:
Net earnings (losses) attributable to common shares	(44,948)					(45,035)			87
Other comprehensive loss	50,984						51,017		(33)
Ending balance at Dec. 31, 2017	698,836	0	1,024	181	985,566	13,278	(301,322)	(181)	290
Increase (Decrease) in Stockholders' Equity
Change in accounting principle	948					948
Restated balance	699,784	0	1,024	181	985,566	14,226	(301,322)	(181)	290
Share-based compensation	5,364				5,364
Exercised stock options and vested share awards	7		7		0
Comprehensive loss:
Net earnings (losses) attributable to common shares	(28,252)					(28,456)			204
Other comprehensive loss	(36,642)						(36,897)		255
Ending balance at Dec. 31, 2018	$ 640,261	$ 0	$ 1,031	$ 181	$ 990,930	$ (14,230)	$ (338,219)	$ (181)	$ 749