Property, plant and equipment (Tables)

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Statement [Line Items]

Disclosure of detailed information about property, plant and equipment [Table Text Block]

		Exploration
		and		Capital
		evaluation		works in			Mining			Plant and
Dec. 31, 2017		assets		progress			properties			equipment			Total
Cost
Balance, beginning of year	$	15,015	$	844,759		$	1,775,432		$	2,368,658		$	5,003,864
Additions		7,000		156,807			-			26,830			190,637
Capitalized stripping and development		-		-			69,178			-			69,178
Decommissioning and restoration		-		51			5,509			5,101			10,661
Interest capitalized		-		13,149			-			-			13,149
Transfers and other movements		-		(79,671	)		-			79,671			-
Impairment		-		(11,320	)		-			-			(11,320	)
Disposals		-		(13	)		(1,600	)		(9,586	)		(11,199	)
Effects of movement in exchange rates		995		2,955			49,184			47,553			100,687
Other		-		6,814			85			455			7,354
Balance, end of year		23,010		933,531			1,897,788			2,518,682			5,373,011
Accumulated depreciation
Balance, beginning of year		-		-			523,460			614,581			1,138,041
Depreciation for the year		-		-			118,754			182,552			301,306
Disposals		-		-			-			(7,540	)		(7,540	)
Effects of movement in exchange rates		-		-			31,516			28,741			60,257
Other		-		-			(19	)		72			53
Balance, end of year		-		-			673,711			818,406			1,492,117
Net book value	$	23,010	$	933,531		$	1,224,077		$	1,700,276		$	3,880,894

		Exploration
		and		Capital
		evaluation		works in			Mining		Plant and
Dec. 31, 2016		assets		progress			properties		equipment			Total
Cost
Balance, beginning of year	$	14,650	$	812,618		$	1,603,952	$	2,289,556		$	4,720,776
Additions		-		87,505			45,383		15,445			148,333
Capitalized stripping and
development		-		19,666			48,886		-			68,552
Decommissioning and restoration		-		(46	)		1,966		23,036			24,956
Interest capitalized		-		14,705			-		-			14,705
Transfers and other movements		-		(89,506	)		56,848		32,658			-
Disposals		-		(1,501	)		-		(11,089	)		(12,590	)
Effects of movement in exchange rates		365		1,334			18,382		18,897			38,978
Other		-		(16	)		15		155			154
Balance, end of year		15,015		844,759			1,775,432		2,368,658			5,003,864
Accumulated depreciation
Balance, beginning of year		-		-			394,098		436,402			830,500
Depreciation for the year		-		-			119,420		178,175			297,595
Disposals		-		-			-		(9,160	)		(9,160	)
Effects of movement in exchange rates		-		-			9,810		9,076			18,886
Other		-		-			132		88			220
Balance, end of year		-		-			523,460		614,581			1,138,041
Net book value	$	15,015	$	844,759		$	1,251,972	$	1,754,077		$	3,865,823