We had goodwill of $2,470.6 million and $2,394.8 million as of June 30, 2021 and December 31, 2020, respectively. The change in the net carrying amount of goodwill by segment was as follows:

(In millions)	Plumbing		Outdoors & Security		Cabinets		Total Goodwill
Goodwill at December 31, 2020^(a)	$	750.1	$	718.6	$	926.1	$	2,394.8
Year-to-date translation adjustments		3.5		0.7		1.6		5.8
Acquisition-related adjustments		65.5		4.5		—		70.0
Goodwill at June 30, 2021^(a)	$	819.1	$	723.8	$	927.7	$	2,470.6

The gross carrying value and accumulated amortization by class of identifiable intangible assets as of June 30, 2021 and December 31, 2020 were as follows:

(In millions)	As of June 30, 2021							As of December 31, 2020
	Gross Carrying Amounts		Accumulated Amortization			Net Book Value		Gross Carrying Amounts		Accumulated Amortization			Net Book Value
Indefinite-lived tradenames	$	713.6	$	—		$	713.6	$	711.0	$	—		$	711.0
Amortizable intangible assets
Tradenames		37.6		(15.1	)		22.5		34.8		(14.0	)		20.8
Customer and contractual relationships		980.0		(363.9	)		616.1		973.2		(337.3	)		635.9
Patents/proprietary technology		133.0		(64.6	)		68.4		109.6		(57.0	)		52.6
Total		1,150.6		(443.6	)		707.0		1,117.6		(408.3	)		709.3
Total identifiable intangibles	$	1,864.2	$	(443.6	)	$	1,420.6	$	1,828.6	$	(408.3	)	$	1,420.3

We had net identifiable intangible assets of $1,420.6 million and $1,420.3 as of June 30, 2021 and December 31, 2020, respectively. The $35.6 million increase in gross identifiable intangible assets was primarily due to the consolidation of Flo and foreign translation adjustments.

Amortizable identifiable intangible assets, principally customer relationships, are subject to amortization over their estimated useful life, ranging from 2 to 30 years, based on the assessment of a number of factors that may impact useful life, which includes customer attrition rates and other relevant factors.

During the first half of 2021, no events or circumstances occurred that would have required us to perform interim impairment tests of goodwill or indefinite-lived tradenames.

During the second quarter of 2020, we recognized a pre-tax charge of $13.0 million related to a tradename in our Plumbing segment and the remaining carrying value of this tradename is being amortized over its estimated useful life of 30 years. This charge was primarily due to extended closures of luxury plumbing showrooms associated with the impact of the novel coronavirus (“COVID-19”) pandemic that led to lower than expected sales related to an indefinite-lived tradename combined with the updated financial outlook compared to previous forecasts and uncertainty of the COVID-19 pandemic on the sales and profitability.

In the first quarter of 2020, we recognized an impairment charge of $9.5 million related to an indefinite-lived tradename in our Cabinets segment. This charge was primarily the result of lower expected sales of custom cabinetry products related to the impact of COVID-19. As of June 30, 2021, the carrying value of this tradename was $29.1 million.

The fair values of these tradenames were measured using the relief-from-royalty approach, which estimates the present value of royalty income that could be hypothetically earned by licensing the tradename to a third party over its remaining useful life. Some of the more significant assumptions inherent in estimating the fair values include forecasted revenue growth rates for the tradename, assumed royalty rate, and a market-participant discount rate that reflects the level of risk associated with the tradenames’ future revenues and profitability. We selected the assumptions used in the financial forecasts using historical data, supplemented by current and anticipated market conditions, estimated growth rates, and management plans. These assumptions represent Level 3 inputs of the fair value hierarchy (refer to Note 8).

The significant assumptions used to estimate the fair values of the tradenames impaired during the year ended December 31, 2020 were as follows:

	2020
Unobservable Input	Minimum			Maximum			Weighted Average^(a)
Discount rate		14.8	%		15.8	%		15.1	%
Royalty rate^(b)		4.0	%		5.0	%		4.3	%
Long-term revenue growth rate^(c)		1.0	%		3.0	%		1.6	%

As of December 31, 2020, the fair value of four Cabinets' tradenames exceeded their carrying values of $180.6 million by less than 30%. A reduction in the estimated fair value of the tradenames in our Cabinets segment could trigger additional impairment charges in future periods. Events or circumstances that could have a potential negative effect on the estimated fair value of our reporting units and indefinite-lived tradenames include: lower than forecasted revenues, more severe impacts of the COVID-19 pandemic than currently expected, including due to resurgences of the virus, actual new construction and repair and remodel growth rates that fall below our assumptions, actions of key customers, increases in discount rates, continued economic uncertainty, higher levels of unemployment, weak consumer confidence, lower levels of discretionary consumer spending, a decrease in royalty rates and a decline in the trading price of our common stock. We cannot predict the occurrence of certain events or changes in circumstances that might adversely affect the carrying value of goodwill and indefinite-lived assets.