8. CORE DEPOSIT PREMIUM AND MORTGAGE SERVICING RIGHTS

The following table presents changes in core deposit premium and mortgage servicing rights for the six months ended June 30, 2017:



(dollars in thousands)	Core Deposit Premium			Mortgage Servicing Rights			Total
Balance, beginning of period	$	4,680		$	15,779		$	20,459
Additions	—			1,220			1,220
Amortization	(1,337		)	(1,067		)	(2,404		)
Balance, end of period	$	3,343		$	15,932		$	19,275

Income generated as the result of new mortgage servicing rights is reported as gains on sales of loans and totaled $0.6 million and $1.2 million for the three and six months ended June 30, 2017, compared to $0.7 million and $1.2 million for the three and six months ended June 30, 2016.

Amortization of mortgage servicing rights was $0.5 million and $1.1 million for the three and six months ended June 30, 2017, compared to $1.8 million and $3.3 million for the three and six months ended June 30, 2016.

The following table presents the fair market value and key assumptions used in determining the fair market value of our mortgage servicing rights:



	Six Months Ended June 30,
(dollars in thousands)	2017			2016
Fair market value, beginning of period	$	18,087		$	18,345
Fair market value, end of period	17,024			16,123
Weighted average discount rate	9.5		%	9.5		%
Forecasted constant prepayment rate assumption	16.1			16.5

The gross carrying value and accumulated amortization related to our core deposit premium and mortgage servicing rights are presented below:



	June 30, 2017							December 31, 2016
(dollars in thousands)	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Core deposit premium	$	44,642	$	(41,299	)	$	3,343	$	44,642	$	(39,962	)	$	4,680
Mortgage servicing rights	63,269		(47,337		)	15,932		62,049		(46,270		)	15,779
Total	$	107,911	$	(88,636	)	$	19,275	$	106,691	$	(86,232	)	$	20,459

Based on the core deposit premium and mortgage servicing rights held as of June 30, 2017, estimated amortization expense for the remainder of fiscal year 2017, the next five succeeding fiscal years and all years thereafter are as follows:



	Estimated Amortization Expense
(dollars in thousands)	Core Deposit Premium		Mortgage Servicing Rights		Total
2017 (remainder)	$	1,337	$	1,293	$	2,630
2018	2,006		2,148		4,154
2019	—		1,767		1,767
2020	—		1,448		1,448
2021	—		1,201		1,201
2022	—		1,039		1,039
Thereafter	—		7,036		7,036
	$	3,343	$	15,932	$	19,275

We perform an impairment assessment of our core deposit premium and mortgage servicing rights whenever events or changes in circumstance indicate that the carrying value of those assets may not be recoverable. Our impairment assessments involve, among other valuation methods, the estimation of future cash flows and other methods of determining fair value. Estimating future cash flows and determining fair values is subject to judgment and often involves the use of significant estimates and assumptions. The variability of the factors we use to perform our impairment tests depend on a number of conditions, including the uncertainty about future events and cash flows. All such factors are interdependent and, therefore, do not change in isolation. Accordingly, our accounting estimates may materially change from period to period due to changing market factors.