16.	Mortgage Servicing Rights, Net

The changes in the carrying amount of mortgage servicing rights for the three and nine months ended September 30, 2018 and 2017 were as follows (in thousands):

	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Mortgage Servicing Rights
Beginning balance	$	393,383		$	381,908		$	399,349		$	347,558
Additions		33,901			29,549			65,632			98,814
Purchases		516			—			2,124			577
Amortization		(20,850	)		(19,183	)		(60,155	)		(54,675	)
Ending balance	$	406,950		$	392,274		$	406,950		$	392,274
Valuation Allowance
Beginning balance	$	(1,343	)	$	(5,481	)	$	(6,723	)	$	(7,742	)
Decrease (increase)		(366	)		(658	)		5,014			1,603
Ending balance		(1,709	)		(6,139	)		(1,709	)		(6,139	)
Net balance	$	405,241		$	386,135		$	405,241		$	386,135

The amount of contractually specified servicing fees (including primary and special servicing fees) and ancillary fees (including yield maintenance fees) earned by the Company were as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Servicing fees	$	26,143	$	24,721	$	77,367	$	70,505
Escrow interest and placement fees		5,395		2,835		12,229		6,315
Ancillary fees		3,410		1,501		6,611		3,909
Total Servicing fees	$	34,948	$	29,057	$	96,207	$	80,729

The Company’s primary servicing portfolio as of September 30, 2018 and December 31, 2017 was approximately $56.1 billion and $54.2 billion, respectively. Also, the Company is named special servicer for a number of commercial mortgage-backed securitizations. Upon certain specified events (such as, but not limited to, loan defaults and loan assumptions), the administration of the loan is transferred to the Company. The Company’s special servicing portfolio at September 30, 2018 and December 31, 2017 was $3.2 billion and $3.8 billion, respectively.

The estimated fair value of Mortgage servicing rights, net as of September 30, 2018 and December 31, 2017 were $444.9 million and $418.1 million, respectively.

Fair values are estimated using a valuation model that calculates the present value of the future net servicing cash flows. The cash flow assumptions used are based on assumptions the Company believes market participants would use to value the portfolio. Significant assumptions include estimates of the cost of servicing per loan, discount rate, earnings rate on escrow deposits and prepayment speeds. The discount rates used in measuring fair value for the nine months ended September 30, 2018 and for the year ended December 31, 2017 was between 3.0% and 13.5% and varied based on investor type. An increase in discount rate of 100 bps or 200 bps would result in a decrease in fair value by $13.5 million and $25.5 million, respectively, as of September 30, 2018 and by $11.8 million and $23.0 million, respectively, at December 31, 2017.