Goodwill and Other Intangible Assets

Goodwill of $199.8 million and $138.5 million is included in other assets on our Consolidated Balance Sheets as of May 31, 2019, and August 31, 2018, respectively. Goodwill acquired during the third quarter of fiscal 2019 was $61.4 million, related to our acquisition of the remaining 75% ownership interest in West Central Distribution, LLC ("WCD"). See Note 16, Acquisitions, for additional information. Changes in the net carrying amount of goodwill for the nine months ended May 31, 2019, by segment, are as follows:



	Energy		Ag		Corporate and Other		Total
	(Dollars in thousands)
Balances, August 31, 2018	$	552	$	127,338	$	10,574	$	138,464
Goodwill acquired during the period	—		61,358		—		61,358
Balances, May 31, 2019	$	552	$	188,696	$	10,574	$	199,822

No goodwill has been allocated to our Nitrogen Production segment, which consists solely of our CF Nitrogen investment accounted for using the equity method of accounting.

Intangible assets subject to amortization primarily include customer lists, trademarks and non-compete agreements, and are amortized over their respective useful lives (ranging from 2 to 30 years). Intangible assets of $47.2 million were acquired during the nine months ended May 31, 2019, related to the acquisition of the remaining 75% ownership interest in WCD. See Note 16, Acquisitions, for additional information. Information regarding intangible assets that are included in other assets on our Consolidated Balance Sheets is as follows:



	May 31, 2019							August 31, 2018
	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
	(Dollars in thousands)
Customer lists	$	84,815	$	(16,054	)	$	68,761	$	40,815	$	(13,082	)	$	27,733
Trademarks and other intangible assets	9,736		(5,393		)	4,343		6,536		(4,931		)	1,605
Total intangible assets	$	94,551	$	(21,447	)	$	73,104	$	47,351	$	(18,013	)	$	29,338

Total amortization expense for intangible assets during the three and nine months ended May 31, 2019, was $1.9 million and $3.4 million, respectively. Total amortization expense for intangible assets during the three and nine months ended May 31, 2018, was $0.8 million and $2.5 million, respectively. The estimated annual amortization expense related to intangible assets subject to amortization for the next five years is as follows:



	(Dollars in thousands)
Year 1	$	4,540
Year 2	4,487
Year 3	4,187
Year 4	3,944
Year 5	3,940