Employee Benefit Plans - Annual Retirement Plan Expense Assumptions (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Discount rate		4.26%	4.55%
Long-term rate of return on plan assets	5.10%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.71%
Long-term rate of return on plan assets		4.20%	4.50%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.58%
Long-term rate of return on plan assets		4.30%	4.65%