3. Software and Other Intangible Assets

At December 31, 2013, software net book value totaled $191.5 million, net of $95.3 million of accumulated amortization. Included in this amount is software marketed for external sale of $94.0 million. The remaining software net book value of $97.5 million is comprised of various software that has been acquired or developed for internal use.

At December 31, 2012, software net book value totaled $129.3 million, net of $69.4 million of accumulated amortization. Included in this amount is software marketed for external sale of $100.4 million. The remaining software net book value of $28.9 million is comprised of various software that has been acquired or developed for internal use.

Amortization of acquired software marketed for external sale is computed using the greater of the ratio of current revenues to total current and anticipated revenues expected to be derived from the software or the straight-line method over an estimated useful life of generally three to ten years. Software for resale amortization expense recorded during the years ended December 31, 2013, 2012 and 2011 totaled $13.6 million, $13.8 million, and $6.3 million, respectively. These software amortization expense amounts are reflected in cost of license in the consolidated statements of income.

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 amortization expense recorded during the years ended December 31, 2013, 2012 and 2011 totaled $19.1 million, $11.6 million, and $8.1 million, respectively. These software amortization expense amounts are reflected in depreciation and amortization in the consolidated statements of income.

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):


	December 31, 2013							December 31, 2012
	Gross Carrying Amount		Accumulated Amortization			Net Balance		Gross Carrying Amount		Accumulated Amortization			Net Balance
Customer relationships	$	277,356	$	(49,410	)	$	227,946	$	157,364	$	(33,727	)	$	123,637
Purchased contracts		10,865		(10,865	)		—		10,823		(10,549	)		274
Trademarks and tradenames		13,995		(4,383	)		9,612		5,830		(2,096	)		3,734
Covenant not to compete		438		(303	)		135		442		(187	)		255

	$	302,654	$	(64,961	)	$	237,693	$	174,459	$	(46,559	)	$	127,900

Other intangible assets amortization expense recorded during the years ended December 31, 2013, 2012 and 2011 totaled $18.5 million, $12.1 million, and $6.4 million, respectively. Based on capitalized intangible assets at December 31, 2013, and assuming no impairment of these intangible assets, estimated amortization expense amounts in future fiscal years are as follows (in thousands):


Fiscal Year Ending December 31,	Software Amortization		Other Intangible Assets Amortization
2014	$	35,411	$	22,433
2015		29,061		19,103
2016		25,477		18,050
2017		21,288		15,765
2018		20,747		15,255
Thereafter		59,484		147,087

Total	$	191,468	$	237,693