Discontinued operations - Schedule of Disposal Groups Including Discontinued Operations Income Statement (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue									$ 350,241	$ 628,714	$ 613,283
Loss from discontinued operations									(58,434)	(34,255)	(10,974)
Income tax expense									(433)	(1,501)	(1,721)
Loss from discontinued operations, net of income tax									(58,867)	(35,756)	(12,695)
Reclassification of foreign currency translation from accumulated other comprehensive income									(6,711)
Net loss from discontinued operations	1,672	(74,092)	(16,264)	68,493	(15,724)	(10,837)	(4,191)	(5,004)	(20,191)	(35,756)	(12,695)
SCO [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sale of discontinued operations									87,892
Income tax (expense)/ recovery (note 6)									(19,019)
Utilization of net operating loss carry-forwards (note 6)									17,613
Discontinued Operations, sale net of tax									86,486
Reclassification of foreign currency translation from accumulated other comprehensive income									(1,865)
Net gain (loss) on sale of discontinued 0perations									84,621
U.S. LTL [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sale of discontinued operations									(54,521)
Income tax (expense)/ recovery (note 6)									21,743
Valuation allowance (note 6)									(21,743)
Discontinued Operations, sale net of tax									(54,521)
Reclassification of foreign currency translation from accumulated other comprehensive income									8,576
Net gain (loss) on sale of discontinued 0perations									$ (45,945)