Schedule II - Valuation and Qualifying Accounts - LIFO and Inventory Valuation Adjustments (Details) - LIFO Valuation Adjustments - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 12,867	$ 10,556	$ 9,381
Charged to Cost and Expense	2,922	2,311	1,175
Reductions	0	0	0
Other	0	0	0
Balance at end of year	$ 15,789	$ 12,867	$ 10,556