SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Inventories (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Dec. 30, 2017
Accounting Policies [Abstract]
Inventory valued at the lower of cost, determined on the last-in, first-out (LIFO) method, or market (as a percent)	37.00%		37.00%
Excess of replacement cost of inventories over the LIFO value	$ 46,459		$ 43,727
Inventory, Net [Abstract]
Raw materials and purchased parts	191,918		183,029
Work-in-process	19,500		30,671
Finished goods and manufactured goods	217,012		250,975
Subtotal	428,430		464,675
Less: LIFO reserve	46,459		43,727
Net inventory	$ 381,971	$ 384,705	$ 420,948

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The excess of replacement or current cost over the stated LIFO (last in first out) inventory value when the LIFO inventory method is utilized.

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

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Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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The percentage of LIFO (last in first out) inventory to total inventory as of the balance sheet date if other than 100 percent.

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