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 September 30, 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. Goodwill impairment was neither indicated nor recorded during the nine months ended September 30, 2018 or the year ended December 31, 2017.

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.

Intangible assets are being amortized over various periods ranging from 10 to 15 years. The Company recorded $830,000 of intangible assets during 2017 related to the insurance operations in the Hardeman acquisition. The Company recorded $3.8 million of other intangible assets during 2017 as part of the OKSB acquisition which were subsequently sold in first quarter 2018.

The Company’s goodwill and other intangibles (carrying basis and accumulated amortization) at September 30, 2018 and December 31, 2017, were as follows:



(In thousands)	September 30, 2018			December 31, 2017

Goodwill	$	845,687		$	842,651
Core deposit premiums:
Gross carrying amount	105,984			105,984
Accumulated amortization	(23,802		)	(16,659		)
Core deposit premiums, net	82,182			89,325
Books of business intangible:
Gross carrying amount	15,234			15,414
Accumulated amortization	(3,441		)	(2,827		)
Books of business intangible, net	11,793			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	93,975			106,071
Total goodwill and other intangible assets	$	939,662		$	948,722

The Company’s estimated remaining amortization expense on intangibles as of September 30, 2018 is as follows:



(In thousands)	Year	Amortization Expense
	Remainder of 2018	$	2,642
	2019	10,565
	2020	10,552
	2021	10,490
	2022	10,438
	Thereafter	49,288
	Total	$	93,975