Equity - Accumulated other comprehensive income (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($)
Components of Accumulated Other Comprehensive Loss
Balance at December 31, 2015	$ (58,562)
Currency translation adjustment, net of income tax expense of $1,589	2,608
Changes related to benefit plans, net of income tax benefit of $42	(126)
Balance at June 30, 2016	(56,080)
Currency Translation [Member]
Components of Accumulated Other Comprehensive Loss
Balance at December 31, 2015	(57,201)
Currency translation adjustment, net of income tax expense of $1,589	2,608
Changes related to benefit plans, net of income tax benefit of $42	0
Balance at June 30, 2016	(54,593)
Employee Benefit Plans [Member]
Components of Accumulated Other Comprehensive Loss
Balance at December 31, 2015	(1,361)
Currency translation adjustment, net of income tax expense of $1,589	0
Changes related to benefit plans, net of income tax benefit of $42	(126)
Balance at June 30, 2016	$ (1,487)