Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 75,306	$ 93,512	$ 138,575
Adjustments for items not affecting cash:
Depreciation and amortization expenses (note 6)	52,694	40,861	42,032
Impairment loss (note 7)	8,911	28,243
Stock option compensation expense (note 28)	13,700	5,507	4,001
Equity-classified PSU expense (note 28)	3,529	1,981
Inventory write down (note 14)	834	3,084	480
Deferred income tax recovery	(17,268)	(3,359)	(4,559)
Equity loss (income) less dividends received	26	(1,028)	(916)
Unrealized foreign exchange loss	254	1,947	1,403
Change in fair value of contingent consideration	(2,446)	(2,044)
Gain on disposition of property, plant and equipment	(1,656)	(1,282)	(9,691)
Amortization of debt issuance costs	3,056	359
Other, net	349	(905)
Net changes in operating assets and liabilities (note 11)	8,977	10,682	25,134
Net cash provided by operating activities	146,266	177,558	196,459
Investing activities:
Acquisition of contingently redeemable NCI (note 9)		(41,092)
Acquisition of NCI (note 32)		(226)
Acquisition of equity investments			(3,000)
Property, plant and equipment additions	(10,812)	(18,918)	(22,055)
Intangible asset additions	(28,584)	(17,558)	(8,764)
Proceeds on disposition of property, plant and equipment	4,985	6,691	16,667
Other, net	(692)	(248)	(89)
Net cash used in investing activities	(710,954)	(116,862)	(29,348)
Financing activities:
Dividends paid to stockholders (note 27)	(72,785)	(70,459)	(64,340)
Dividends paid to NCI	(41)	(3,436)	(1,340)
Issuances of share capital	9,936	24,338	29,816
Share repurchase (note 27)		(36,726)	(47,489)
Proceeds from short-term debt	6,971	67,584	11,223
Repayment of short-term debt	(24,479)	(57,516)	(6,558)
Proceeds from long-term debt	325,000	647,091
Repayment of long-term debt	(108,985)	(148,158)
Debt issue costs (note 25)	(12,624)	(10,644)
Debt extinguishment costs		(6,787)
Repayment of finance lease obligations	(2,322)	(1,655)	(2,073)
Other, net	(106)	511	72
Net cash provided by (used in) financing activities	120,565	404,143	(80,689)
Effect of changes in foreign currency rates on cash, cash equivalents, and restricted cash	17,150	4	(26,265)
Increase (decrease)	(426,973)	464,843	60,157
Beginning of period	758,089	293,246	233,089
Cash, cash equivalents, and restricted cash, end of period (note 11)	331,116	758,089	293,246
Iron Planet Holdings Inc. [Member]
Investing activities:
Acquisition (note 32)	$ (675,851)
Mascus International Holdings BV [Member]
Investing activities:
Acquisition (note 32)		(28,123)
Xcira LLC [Member]
Investing activities:
Acquisition (note 32)			$ (12,107)
Petrowsky Auctioneers Inc. [Member]
Investing activities:
Acquisition (note 32)		(6,250)
Kramer Auctions Ltd. [Member]
Investing activities:
Acquisition (note 32)		$ (11,138)