6. Software and Other Intangible Assets

At September 30, 2013, software net book value totaling $176.3 million, net of $87.2 million of accumulated amortization, includes the net book value of software marketed for external sale of $96.8 million. The remaining software net book value of $79.5 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 September 30, 2013 and 2012 totaled $3.4 million and $3.8 million, respectively. Software for resale amortization expense recorded in the nine months ended September 30, 2013 and 2012 totaled $10.1 million and $10.0 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 $5.0 million and $3.0 million for the three months ended September 30, 2013 and 2012, respectively, is included in depreciation and amortization in the condensed consolidated statements of operations. Amortization of software for internal use was $12.8 million and $8.5 million for the nine months ended September 30, 2013 and 2012, respectively.

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 (in thousands):


	September 30, 2013							December 31, 2012
	Gross Carrying Amount		Accumulated Amortization			Net Balance		Gross Carrying Amount		Accumulated Amortization			Net Balance
Customer relationships	$	230,112	$	(44,875	)	$	185,237	$	157,364	$	(33,727	)	$	123,637
Purchased contracts		10,826		(10,826	)		—		10,823		(10,549	)		274
Trademarks and tradenames		8,897		(3,708	)		5,189		5,830		(2,096	)		3,734
Covenant not to compete		439		(274	)		165		442		(187	)		255

	$	250,274	$	(59,683	)	$	190,591	$	174,459	$	(46,559	)	$	127,900

Other intangible assets amortization expense for the three months ended September 30, 2013 and 2012 totaled $4.7 million and $3.2 million, respectively. Other intangible assets amortization expense for the nine months ended September 30, 2013 and 2012 totaled $13.3 million and $8.7 million, respectively.

Based on capitalized software and other intangible assets at September 30, 2013, estimated amortization expense for future fiscal years is as follows (in thousands):


Fiscal Year Ending December 31,	Software Amortization		Other Intangible Assets Amortization
Remainder of 2013	$	8,771	$	4,737
2014		32,075		17,600
2015		26,017		14,273
2016		22,204		13,299
2017		18,612		12,626
2018		17,840		12,116
Thereafter		50,744		115,940

Total	$	176,263	$	190,591