Condensed Consolidated Statements of Changes in Equity - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Common stock [Member]	Additional paid-In capital [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Non-controlling interest [Member]	Performance Share Units [Member]	Total
Balance at Dec. 31, 2016	$ 125,474	$ 27,638	$ 601,071	$ (67,126)	$ 4,773		$ 691,830
Balance, shares at Dec. 31, 2016	106,822,001
Contingently redeemable Performance share units, Balance at Dec. 31, 2016						$ 3,950	3,950
Net income			10,377		56		10,433
Other comprehensive income				7,436	4		7,440
Comprehensive income			10,377	7,436	60		17,873
Stock option exercises	$ 4,151	(739)					3,412
Stock option exercises, shares	132,950
Stock option compensation expense (note 20)		1,311					1,311
Equity-classified PSU expense (note 20)		15				997	15
Equity-classified PSU dividend equivalents		2	(47)			45	(45)
Change in value of contingently redeemable equity-classified PSUs			(29)			29	(29)
Cash dividends paid (note 19)			(18,160)		(41)		(18,201)
Balance at Mar. 31, 2017	$ 129,625	$ 28,227	$ 593,212	$ (59,690)	$ 4,792		696,166
Balance, shares at Mar. 31, 2017	106,954,951
Contingently redeemable Performance share units, Balance at Mar. 31, 2017						$ 5,021	$ 5,021