Environmental Matters - Summary of Environment Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Environmental Exit Cost [Line Items]
Balance at beginning of year	$ 32,867	$ 31,467
Obligations settled	(123)	(116)
Balance at end of year	35,777	32,867
Current portion, included within accrued expenses and other current liabilities	188	120
Asset retirement obligations	35,589	32,747
Environmental Restoration Costs [Member]
Environmental Exit Cost [Line Items]
Balance at beginning of year	3,614	3,537
Provision for new environmental losses	292	918
Changes in estimates for previously incurred losses	354	104
Obligations settled	(870)	(945)
Balance at end of year	3,390	3,614
Current portion, included within accrued expenses and other current liabilities	1,520	1,450
Asset retirement obligations	$ 1,870	$ 2,164