Property, Plant and Equipment

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

5. Property, Plant and Equipment

Property, plant and equipment as of December 31, 2017 and 2016 are comprised of the following (in thousands):

	December 31,
	2017			2016
Buildings and related structures	$	69,958		$	64,939
Machinery and equipment		308,713			255,618
Others		42,497			29,492
		421,168			350,049
Less: accumulated depreciation		(231,356	)		(184,521	)
Land		16,091			14,265
Property, plant and equipment, net	$	205,903		$	179,793

Aggregate depreciation expenses totaled $27,498 thousand and $24,941 thousand for the years ended December 31, 2017 and 2016, respectively.

In December 2017, a portion of the Company’s real estate was pledged as collateral in connection with a payment plan for taxes and penalties assessed by the Korean National Tax Service (the “KNTS”) as a result of a tax audit. For further description of the tax audit, see Note 17, “Income Taxes—Other Matter”.