Equity - Accumulated other comprehensive income (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Components of Accumulated Other Comprehensive Loss
Balance at December 31, 2015	$ (58,562)
Currency translation adjustment, net of income tax benefit of $2,508	(4,114)
Changes related to benefit plans, net of income tax expense of $2	5
Balance at March 31, 2016	(62,671)
Currency Translation [Member]
Components of Accumulated Other Comprehensive Loss
Balance at December 31, 2015	(57,201)
Currency translation adjustment, net of income tax benefit of $2,508	(4,114)
Changes related to benefit plans, net of income tax expense of $2	0
Balance at March 31, 2016	(61,315)
Employee Benefit Plans [Member]
Components of Accumulated Other Comprehensive Loss
Balance at December 31, 2015	(1,361)
Currency translation adjustment, net of income tax benefit of $2,508	0
Changes related to benefit plans, net of income tax expense of $2	5
Balance at March 31, 2016	$ (1,356)