Employee Benefit Plans - Fair Value Measurements (Details) - Pension - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Investments at Fair Value:	$ 50,949	$ 57,377	$ 51,114
Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Investments at Fair Value:	0	8,986
Mutual Funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Investments at Fair Value:	0	8,986
Mutual Funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Investments at Fair Value:	0	0
Mutual Funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Investments at Fair Value:	0	0
Separate Investment Accounts
Defined Benefit Plan Disclosure [Line Items]
Investments at Net Asset Value:	$ 50,949	$ 48,391