Employee Benefit Plans - Schedule of Allocation of Plan Assets (Details)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	100.00%	100.00%
Common collective trusts
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	60.00%	62.00%
Corporate bonds (S&P rating of A or higher)
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	6.00%	6.00%
Corporate bonds (S&P rating of lower than A)
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	14.00%	12.00%
US Treasury and Government
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	13.00%	13.00%
Mortgage-backed securities
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	5.00%	5.00%
Municipal bonds
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	0.00%	1.00%
Money market fund
Defined Benefit Plan Disclosure [Line Items]
Plan asset allocation percentage	2.00%	1.00%