GOODWILL AND OTHER INTANGIBLE ASSETS

Goodwill is tested annually, or more often than annually, if circumstances warrant, for impairment. If the implied fair value of goodwill is lower than its carrying amount, goodwill impairment is indicated, and goodwill is written down to its implied fair value. Subsequent increases in goodwill value are not recognized in the financial statements. Goodwill totaled $845.7 million at December 31, 2018 and $842.7 million at December 31, 2017.

The Company recorded $229.1 million, $240.8 million and $29.4 million of goodwill as a result of its acquisitions of OKSB, First Texas and Hardeman, respectively, partially offset by $4.1 million due to the sale of the Company’s property and casualty insurance lines of business during the third quarter 2017. The Company recorded $21.5 million of goodwill during 2016 as a result of its Citizens acquisition. Goodwill impairment was neither indicated nor recorded in 2018, 2017 or 2016. The goodwill recorded in the Citizens acquisition will be deductible for tax purposes.

Core deposit premiums are amortized over periods ranging from 10 to 15 years and are periodically evaluated, at least annually, as to the recoverability of their carrying value. Core deposit premiums of $42.1 million, $7.3 million, and $7.8 million were recorded during 2017 as part of the OKSB, First Texas and Hardeman acquisitions, respectively. Core deposit premiums of $5.1 million were recorded in 2016 as part of the Citizens acquisition.

Intangible assets are being amortized over various periods ranging from 10 to 15 years. The Company recorded $830,000 and $3.8 million of intangible assets during 2017 related to the insurance operations in the Hardeman acquisition and the OKSB acquisition, respectively. The Company recorded $591,000 of intangible assets during 2016 related to the trust operations acquired in the Citizens acquisition. Intangible assets decreased by $1.3 million due to the sale of insurance lines of business during the third quarter of 2017 and decreased $3.8 million due to the sale of the OKSB intangible asset in the first quarter of 2018.

The Company’s goodwill and other intangibles (carrying basis and accumulated amortization) at December 31, 2018 and 2017 were as follows:



(In thousands)	2018			2017
Goodwill	$	845,687		$	842,651
Core deposit premiums:
Gross carrying amount	105,984			105,984
Accumulated amortization	(26,177		)	(16,659		)
Core deposit premiums, net	79,807			89,325
Books of business intangible:
Gross carrying amount	15,234			15,414
Accumulated amortization	(3,707		)	(2,827		)
Books of business intangible, net	11,527			12,587
Other intangibles:
Gross carrying amount	2,068			6,037
Accumulated amortization	(2,068		)	(1,878		)
Other intangibles, net	—			4,159
Other intangible assets, net	91,334			106,071
Total goodwill and other intangible assets	$	937,021		$	948,722

Core deposit premium amortization expense recorded for the years ended December 31, 2018, 2017 and 2016 was $9.5 million, $6.0 million and $4.4 million, respectively. Amortization expense recorded for purchased credit card relationships for the year ended December 31, 2018 was $310,000 and $414,000 for the years ended December 31, 2017 and 2016. Book of business amortization expense recorded for the years ended December 31, 2018, 2017 and 2016 was $1.1 million.

The Company’s estimated remaining amortization expense on intangibles as of December 31, 2018 is as follows:



Year	(In thousands)
2019	$	10,565
2020	10,552
2021	10,490
2022	10,438
2023	10,156
Thereafter	39,133
Total	$	91,334