Goodwill and Core Deposit Intangibles

Management analyzes its goodwill for impairment on an annual basis and between annual tests in certain circumstances, such as upon material adverse changes in legal, business, regulatory and economic factors. An impairment loss is recorded to the extent that the carrying amount of goodwill exceeds its implied fair value. The Company performed an impairment assessment as of July 1, 2018 and 2017 and concluded that there was no impairment to goodwill.

Goodwill



	As of September 30,
	2018		2017
Net carrying value at beginning of nine month period	$	444.7	$	212.8
Addition to provisional goodwill from acquisition	100.8		232.2
Measurement period adjustment to previously recorded goodwill	0.9		—
Net carrying value at end of period	$	546.4	$	445.0

Core deposit intangibles (“CDI”)



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
CDI, net, beginning of period	$	45.6		$	52.8		$	49.1		$	9.6
Established through acquisitions or provisional adjustments	15.7			—			15.7			48.0
Reductions due to sale of accounts	—			—			—			(3.1		)
CDI current period amortization	(2.0		)	(1.9		)	(5.5		)	(3.6		)
Total CDI, net, end of period	$	59.3		$	50.9		$	59.3		$	50.9

CDI are evaluated for impairment if events and circumstances indicate a possible impairment. The CDI are amortized using an accelerated method based on the estimated weighted average useful lives of the related deposits, which is generally ten years.

The following table provides the estimated future CDI amortization expense:



Years Ending December 31,
2018 remaining	$	2.4
2019	8.9
2020	8.1
2021	7.5
2022	6.9
Thereafter	25.5
Total	$	59.3