Pension and Employee Benefit Plans - Fair value of Funded Plan assets by major category (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	$ 12,595	$ 14,308
Money market fund
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	1,033	516
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	4,881	526
U.S. Treasuries
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	4,465
Corporate stocks
Defined Benefit Plan Disclosure [Line Items]
Total plan assets		1,346
Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	2,216	11,920
Level 1
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	11,562	13,792
Level 1 | Money market fund
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	0
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	4,881	526
Level 1 | U.S. Treasuries
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	4,465
Level 1 | Corporate stocks
Defined Benefit Plan Disclosure [Line Items]
Total plan assets		1,346
Level 1 | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	2,216	11,920
Level 2
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	1,033	516
Level 2 | Money market fund
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	1,033	516
Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	0
Level 2 | U.S. Treasuries
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0
Level 2 | Corporate stocks
Defined Benefit Plan Disclosure [Line Items]
Total plan assets		0
Level 2 | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	0
Level 3 | Money market fund
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	0
Level 3 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0	0
Level 3 | U.S. Treasuries
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	0
Level 3 | Corporate stocks
Defined Benefit Plan Disclosure [Line Items]
Total plan assets		0
Level 3 | Exchange traded funds
Defined Benefit Plan Disclosure [Line Items]
Total plan assets	$ 0	$ 0