Schedule of net deferred tax liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net deferred tax liabilities
Operating loss carry-forwards	$ 122,500	$ 93,466	$ 61,708
Pensions	321	1,899	2,161
Share-based compensation	3,146	2,813	1,647
Trademarks	5,075	5,563	3,868
Other	9,173	9,197	2,897
Less: Valuation allowance	(110,780)	(97,376)	(50,746)
Net deferred tax assets	29,435	15,562	21,535
Other	(7,962)	(5,267)	(4,609)
Property, plant and equipment	(183,174)	(171,016)	(172,643)
Deferred tax liabilities	(191,136)	(176,283)	(177,252)
Net deferred tax liabilities	$ (161,701)	$ (160,721)	$ (155,717)