Condensed Consolidated Statements of Changes in Equity - 6 months ended Jun. 30, 2017 - USD ($) $ in Thousands	Common stock [Member]	Additional paid-in capital ("APIC") [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Non-controlling interest ("NCI") [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			28,012		134		28,146
Other comprehensive income				16,777	36		16,813
Comprehensive income			28,012	16,777	170		44,959
Stock option exercises	$ 7,390	(1,357)					6,033
Stock option exercises, shares	256,511
Stock option compensation expense (note 20)		8,076					8,076
Assumption of stock options on acquisition of IronPlanet (note 22)		2,330					2,330
Modification of PSUs (note 20)			(382)			1,803	(382)
Equity-classified PSU expense (note 20)		260				1,785	260
Equity-classified PSU dividend equivalents		16	(108)			92	(92)
Change in value of contingently redeemable equity-classified PSUs			(76)			76	(76)
Cash dividends paid (note 19)			(36,348)		(41)		(36,389)
Balance at Jun. 30, 2017	$ 132,864	$ 36,963	$ 592,169	$ (50,349)	$ 4,902		716,549
Balance, shares at Jun. 30, 2017	107,078,512
Contingently redeemable Performance share units, Balance at Jun. 30, 2017						$ 7,706	$ 7,706