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 (Previously Reported) at Dec. 31, 2014	$ 762,261	$ 0	$ 1,040	$ 181	$ 1,000,803	$ 5,763	$ (246,420)	$ (181)	$ 1,075
Beginning balance (Adjustments) at Dec. 31, 2014						5,562	(5,562)
Beginning balance at Dec. 31, 2014	762,261	0	1,040	181	1,000,803	11,325	(251,982)	(181)	1,075
Increase (Decrease) in Stockholders' Equity
Share-based compensation	6,707				6,707
Exercised stock options and vested share awards	35		8		27
Repurchase of shares	(38,007)		(33)		(32,118)	(5,856)
Dividend to non-controlling interest	(26)								(26)
Comprehensive income:
Net earnings (losses) attributable to common shares	15,854					16,265			(411)
Other comprehensive income	(88,399)						(88,122)		(277)
Ending 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 income:
Net earnings (losses) attributable to common shares	36,433					36,324			109
Other comprehensive income	(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
Repurchase of shares	0		0		0	0
Dividend to non-controlling interest	(146)								(146)
Comprehensive income:
Net earnings (losses) attributable to common shares	(44,948)					(45,035)			87
Other comprehensive income	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