The Company has approximately $6.3 billion of goodwill and $3.0 billion of identified intangible assets at December 31, 2018.

	Wellbore Technologies			Completion & Production Solutions			Rig Technologies			Total
Balance at December 31, 2016	$	2,874		$	2,058		$	1,135		$	6,067
Goodwill acquired and adjusted during period		37			41			11			89
Currency translation adjustments		45			23			3			71
Balance at December 31, 2017	$	2,956		$	2,122		$	1,149		$	6,227
Goodwill acquired and adjusted during period		64			(33	)		71			102
Currency translation adjustments		(9	)		(48	)		(8	)		(65	)
Balance at December 31, 2018 (1)	$	3,011		$	2,041		$	1,212		$	6,264

(1)

Accumulated goodwill impairment was $2,457 million as of December 31, 2018.

Identified intangible assets with determinable lives consist primarily of customer relationships, trademarks, trade names, patents, and technical drawings acquired in acquisitions, and are being amortized in a manner consistent with the underlying cash flows over the estimated useful lives of 2-30 years. Amortization expense of identified intangibles is expected to be approximately $336 million, $319 million, $308 million, $302 million, and $280 million for the next five years. Included in intangible assets are $383 million of indefinite-lived trade names.

The net book values of identified intangible assets are identified by segment as follows (in millions):

	Wellbore Technologies			Completion & Production Solutions			Rig Technologies			Total
Balance at December 31, 2016	$	2,064		$	1,191		$	275		$	3,530
Additions to intangible assets		18			41			2			61
Amortization		(208	)		(108	)		(23	)		(339	)
Currency translation adjustments		9			36			4			49
Balance at December 31, 2017	$	1,883		$	1,160		$	258		$	3,301
Additions to intangible assets		41			3			55			99
Amortization		(201	)		(111	)		(29	)		(341	)
Currency translation adjustments		12			(47	)		(4	)		(39	)
Balance at December 31, 2018	$	1,735		$	1,005		$	280		$	3,020

Identified intangible assets by major classification consist of the following (in millions):

	Gross		Accumulated Amortization			Net Book Value
December 31, 2017:
Customer relationships	$	4,074	$	(2,118	)	$	1,956
Trademarks		885		(317	)		568
Patents		602		(384	)		218
Indefinite-lived trade names		384		—			384
Other		499		(324	)		175
Total identified intangibles	$	6,444	$	(3,143	)	$	3,301
December 31, 2018:
Customer relationships	$	4,078	$	(2,352	)	$	1,726
Trademarks		891		(341	)		550
Patents		661		(414	)		247
Indefinite-lived trade names		383		—			383
Other		491		(377	)		114
Total identified intangibles	$	6,504	$	(3,484	)	$	3,020

Goodwill represents the excess of cost over the fair value of net assets acquired. Goodwill and intangibles with indefinite lives are not amortized. Goodwill is assigned to the reporting units that are expected to benefit from the synergies of a business combination. The recoverability of goodwill and indefinite-lived intangibles is assessed annually, or more frequently as needed when events or changes have occurred that would suggest an impairment of carrying value, by determining whether the fair values of the applicable reporting units exceed their carrying values.

The impairment analysis compares the reporting unit’s carrying value to the respective fair value. Fair value of the reporting unit is determined using significant unobservable inputs, or level 3 in the fair value hierarchy. These inputs are based on internal management estimates, forecasts and judgments, using discounted cash flow.

The discounted cash flow is based on management’s forecast of operating performance for the reporting unit. The two main assumptions used in measuring goodwill impairment, which bear the risk of change and could impact the Company’s goodwill impairment analysis, include the cash flow from operations from each reporting unit and its weighted average cost of capital. The starting point for each of the reporting unit’s cash flow from operations is the detailed annual plan or updated forecast. Cash flows beyond the updated forecasted operating plans were estimated using a terminal value calculation, which incorporated historical and forecasted financial cyclical trends for each reporting unit and considered long-term earnings growth rates. The financial and credit market volatility directly impacts our fair value measurement through our weighted average cost of capital that we use to determine our discount rate. During times of volatility, significant judgment must be applied to determine whether credit changes are a short-term or long-term trend.

In 2018, based on the annual impairment test, the calculated fair values for all of the Company’s reporting units were substantially in excess of the respective reporting unit’s carrying value with the exception of the Company’s Floating Production Systems business unit. Further deterioration in the offshore turret mooring systems and topside process modules market could lead to an impairment. This business unit has approximately $277 million in goodwill.

In July 2016, as a result of market indicators identified in the third quarter, the Company completed a step one impairment analysis for its Rig Offshore reporting unit and calculated a fair value below its carrying value requiring a step two analysis. The analysis compares the implied fair value of goodwill of a reporting unit to the carrying value of goodwill for the reporting unit. The implied fair value of goodwill is determined by deducting the fair value of a reporting unit’s identifiable assets and liabilities from the fair value of that reporting unit as a whole. Based on the step two analysis performed for the Rig Offshore reporting unit, the Company recorded a $972 million write-down of goodwill during the third quarter.

Management reviews finite-lived intangibles for indicators of impairment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. Cash flows expected to be generated by the finite-lived intangibles are estimated over the intangible asset’s useful life based on updated projections on an undiscounted basis. If the evaluation indicates that the carrying value of the finite-lived intangible asset may not be recoverable, the potential impairment is measured at fair value.