Employee Benefit Plans - Assumptions Used To Determine Net Periodic Benefit Expense (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost
Discount rate	1.80%	2.40%	1.70%
Expected return on plan assets	1.50%	1.50%	1.50%
Rate of compensation increase	2.80%	2.80%	3.00%