GOODWILL AND OTHER INTANGIBLE ASSETS

The Company's annual goodwill impairment test was performed as of October 1, 2018. It was determined that no impairment existed as of that date or as of December 31, 2018. For a discussion of the accounting policies for goodwill and other intangible assets, see Note 1, "Summary of Significant Accounting Policies."

The following table presents changes in the carrying amount of goodwill for the years ended December 31, 2018, 2017, and 2016.

Changes in the Carrying Amount of Goodwill

(Dollar amounts in thousands)



	Years Ended December 31,
	2018		2017		2016
Beginning balance	$	697,608	$	340,879	$	319,007
Acquisitions	31,201		356,729		21,872
Ending balance	$	728,809	$	697,608	$	340,879

The increase in goodwill for the year ended December 31, 2018 resulted from the Northern States acquisition and measurement period adjustment related to finalizing the fair values of the assets acquired and liabilities assumed in the Premier acquisition. During the year ended December 31, 2017 the increase resulted from the Standard and Premier acquisitions and measurement period adjustments related to the NI Bancshares acquisition. During the year ended December 31, 2016, the increase in goodwill resulted from the NI Bancshares acquisition and measurement period adjustments related to the Peoples Bancorp, Inc. acquisition. See Note 3, "Acquisitions," for additional detail regarding transactions completed in 2018 and 2017.

The Company's other intangible assets consist of core deposit intangibles and trust department customer relationship intangibles, which are being amortized over their estimated useful lives. Other intangible assets are subject to impairment testing when events or circumstances indicate that its carrying amount may not be recoverable. The increase in other intangible assets for the year ended December 31, 2018 resulted from the Northern States acquisition. The increase in other intangible assets for the year ended December 31, 2017 resulted from the Standard and Premier acquisitions. During 2018 there were no events or circumstances to indicate impairment.

Other Intangible Assets

(Dollar amounts in thousands)



	Years Ended December 31,
	2018							2017							2016
	Gross		Accumulated Amortization		Net			Gross		Accumulated Amortization		Net			Gross		Accumulated Amortization		Net
Beginning balance	$	97,976	$	40,827	$	57,149		$	58,959	$	32,962	$	25,997		$	48,550	$	28,280	$	20,270
Additions	12,230		—		12,230			39,017		—		39,017			10,409		—		10,409
Amortization expense	—		7,444		(7,444		)	—		7,865		(7,865		)	—		4,682		(4,682		)
Ending balance	$	110,206	$	48,271	$	61,935		$	97,976	$	40,827	$	57,149		$	58,959	$	32,962	$	25,997
Weighted-average remaining life (in years)					7.8							8.3							7.6
Estimated remaining useful lives (in years)					0.7 to 9.8							0.2 to 9.3							0.6 to 9.3

Scheduled Amortization of Other Intangible Assets

(Dollar amounts in thousands)



	Total
Year Ending December 31,
2019	$	8,296
2020	8,246
2021	8,170
2022	8,090
2023	7,713
2024 and thereafter	21,420
Total	$	61,935