Employee Benefit Plans (Details 2) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee benefits plans
Fair value of plan assets	$ 107,862	$ 126,013	$ 116,725
Funded pension plan assets, by asset category (as a percent)	100.00%	100.00%
Total investments, excluding investments valued at NAV
Employee benefits plans
Fair value of plan assets	$ 93,518	$ 100,672
Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefits plans
Fair value of plan assets	93,518	100,672
Significant Other Observable Inputs (Level 2)
Employee benefits plans
Fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3)
Employee benefits plans
Fair value of plan assets	0	0
Equity securities
Employee benefits plans
Fair value of plan assets	$ 71,384	$ 80,191
Funded pension plan assets, by asset category (as a percent)	66.00%	64.00%
Equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefits plans
Fair value of plan assets	$ 71,384	$ 80,191
Equity securities | Significant Other Observable Inputs (Level 2)
Employee benefits plans
Fair value of plan assets	0	0
Equity securities | Significant Unobservable Inputs (Level 3)
Employee benefits plans
Fair value of plan assets	0	0
Debt securities
Employee benefits plans
Fair value of plan assets	$ 22,134	$ 20,481
Funded pension plan assets, by asset category (as a percent)	21.00%	16.00%
Debt securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Employee benefits plans
Fair value of plan assets	$ 22,134	$ 20,481
Debt securities | Significant Other Observable Inputs (Level 2)
Employee benefits plans
Fair value of plan assets	0	0
Debt securities | Significant Unobservable Inputs (Level 3)
Employee benefits plans
Fair value of plan assets	0	0
Other
Employee benefits plans
Fair value of plan assets	$ 14,344	$ 25,341
Funded pension plan assets, by asset category (as a percent)	13.00%	20.00%
Other | NAV
Employee benefits plans
Fair value of plan assets	$ 14,344	$ 25,341