16.	Mortgage Servicing Rights, Net

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

	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Mortgage Servicing Rights
Beginning balance	$	386,953		$	359,189		$	399,349		$	347,558
Additions		25,342			40,459			31,731			69,265
Purchases		1,099			577			1,608			577
Amortization		(20,011	)		(18,317	)		(39,305	)		(35,492	)
Ending balance	$	393,383		$	381,908		$	393,383		$	381,908

Valuation Allowance
Beginning balance	$	(5,427	)	$	(4,574	)	$	(6,723	)	$	(7,742	)
Decrease (increase)		4,084			(907	)		5,380			2,261
Ending balance		(1,343	)		(5,481	)		(1,343	)		(5,481	)
Net balance	$	392,040		$	376,427		$	392,040		$	376,427

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 June 30,				Six Months Ended June 30,
	2018		2017			2018		2017
Servicing fees	$	26,092	$	23,734		$	51,224	$	45,784
Escrow interest and placement fees		3,867		2,021			6,834		3,480
Ancillary fees		2,374		1,085			3,201		2,408
Total Servicing fees	$	32,333	$	26,840		$	61,259	$	51,672

The Company’s primary servicing portfolio as of June 30, 2018 and December 31, 2017 was approximately $55.6 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 June 30, 2018 and December 31, 2017 was $3.4 billion and $3.8 billion, respectively.

The estimated fair value of Mortgage servicing rights, net as of June 30, 2018 and December 31, 2017 were $435.1 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 six months ended June 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 $12.2 million and $23.8 million, respectively, as of June 30, 2018 and by $11.8 million and $23.0 million, respectively, at December 31, 2017.