Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefit Plan Obligations (Textual) [Abstract]
Company's expense for its defined contribution plans	$ 7,300	$ 7,800	$ 8,700
Pension settlement charge, net of cash contributed	$ 0	$ 0	48,344
Other (income) and expenses, net
Employee Benefit Plan Obligations (Textual) [Abstract]
Pension settlement charges			31,900
Pension settlement charge, net of cash contributed			$ 51,400