5. Software and Other Intangible Assets

At March 31, 2014, software net book value totaling $193.1 million, net of $103.2 million of accumulated amortization, includes the net book value of software marketed for external sale of $90.8 million. The remaining software net book value of $102.3 million is comprised of various software that has been acquired or developed for internal use.

Quarterly amortization of software marketed for external sale is computed using the greater of the ratio of current revenues to total estimated revenues expected to be derived from the software or the straight-line method over an estimated useful life of three to ten years. Software for resale amortization expense recorded in the three months ended March 31, 2014 and 2013 totaled $3.5 million and $3.2 million, respectively. These software amortization expense amounts are reflected in cost of software license fees in the condensed consolidated statements of operations.

Quarterly amortization of software for internal use is computed using the straight-line method over an estimated useful life of three to ten years. Software for internal use includes software acquired through acquisitions that is used to provide certain of our hosted offerings. Amortization of software for internal use of $5.2 million and $3.4 million for the three months ended March 31, 2014 and 2013, respectively, is included in depreciation and amortization in the condensed consolidated statements of operations.

The carrying amount and accumulated amortization of the Company’s other intangible assets that were subject to amortization at each balance sheet date are as follows:


	March 31, 2014							December 31, 2013
	Gross							Gross
	Carrying		Accumulated					Carrying		Accumulated
(in thousands)	Amount		Amortization			Net Balance		Amount		Amortization			Net Balance
Customer relationships	$	280,295	$	(55,152	)	$	225,143	$	277,356	$	(49,410	)	$	227,946
Trademarks and tradenames		12,138		(5,333	)		6,805		13,995		(4,383	)		9,612
Covenant not to compete		438		(333	)		105		438		(303	)		135
Purchased Contracts		10,880		(10,880	)		—		10,865		(10,865	)		—

	$	303,751	$	(71,698	)	$	232,053	$	302,654	$	(64,961	)	$	237,693

Other intangible assets amortization expense for the three months ended March 31, 2014 and 2013 totaled $6.5 million and $3.8 million, respectively.

Based on capitalized software and other intangible assets at March 31, 2014, estimated amortization expense for future fiscal years is as follows:


			Other
			Intangible
	Software		Assets
Fiscal Year Ending December 31,	Amortization		Amortization
(in thousands)
Remainder of 2014	$	27,839	$	17,184
2015		31,507		19,883
2016		27,475		18,729
2017		21,818		17,166
2018		20,357		16,656
2019		18,469		16,335
Thereafter		45,665		126,100

Total	$	193,130	$	232,053