We have assigned goodwill to each of our reporting units (as that term is defined in ASC Topic 350-20-20, Goodwill) which corresponds to our operating segments. All of our goodwill related to our Chemicals Segment is from our various step acquisitions of NL and Kronos which occurred prior to 2015, as goodwill was determined prior to the adoption of the equity transaction framework provisions of ASC Topic 810. Substantially all of the net goodwill related to the Component Products Segment was generated from CompX’s acquisitions of certain business units and the step acquisitions of CompX. The Component Products Segment goodwill is assigned to the security products reporting unit within that operating segment.

	Operating segment
	Chemicals		Component Products		Total
		(In millions)
Balance at December 31, 2016, 2017 and 2018	$	352.6	$	27.1	$	379.7

We test for goodwill impairment at the reporting unit level. In determining the estimated fair value of the reporting units, we use appropriate valuation techniques, such as discounted cash flows and, with respect to our Chemicals Segment, we consider quoted market prices, a Level 1 input, while discounted cash flows are a Level 3 input. We also consider control premiums when assessing fair value using quoted market prices. If the carrying amount of the reporting unit’s net assets exceeds its fair value, an impairment charge is recorded for the amount by which such carrying amount exceeds the reporting unit’s fair value (not to exceed the amount of goodwill recognized). We review goodwill for each of our reporting units for impairment during the third quarter of each year. Goodwill is also evaluated for impairment at other times whenever an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying value. If the fair value of an evaluated asset is less than its book value, the asset is written down to fair value.

In 2016, 2017 and 2018, no goodwill impairment was indicated as part of our annual impairment review of goodwill. As permitted by GAAP, during 2017 and 2018 we used the qualitative assessment of ASC 350-20-35 for our Component Products security products reporting unit’s annual impairment test and determined it was not necessary to perform a quantitative goodwill impairment test. During 2016, we used the quantitative assessment of ASC 350-20-35 for security products reporting unit’s annual impairment test using discounted cash flows to determine the estimated fair value of our security products reporting unit. Such discounted cash flows are a Level 3 input as defined by ASC 820-10-35.

Prior to 2016, we recorded an aggregate $16.5 million goodwill impairment, mostly with respect to our Component Products Segment. Our consolidated gross goodwill at December 31, 2018 is $396.2 million.