Property and Equipment

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Property and Equipment

Property and Equipment

Property and equipment consisted of the following as of December 31, 2014 and 2013 (dollars in thousands):

	December 31, 2014			December 31, 2013			Estimated Useful Life in Years
Computer and networking equipment	$	850,533		$	737,957		3-4
Purchased software	46,537			40,237			3
Furniture and fixtures	27,923			20,838			5
Office equipment	14,035			10,353			3
Leasehold improvements	92,544			64,471			2-12
Internal-use software	448,777			340,421			2-7
Property and equipment, gross	1,480,349			1,214,277
Accumulated depreciation and amortization	(878,758		)	(763,990		)
Property and equipment, net	$	601,591		$	450,287

Depreciation and amortization expense on property and equipment and capitalized internal-use software for the years ended December 31, 2014, 2013 and 2012 was $215.3 million, $162.9 million and $183.2 million, respectively. During the years ended December 31, 2014, 2013 and 2012, the Company capitalized $15.2 million, $12.3 million and $9.3 million, respectively, of stock-based compensation related to employees who developed and enhanced internal-use software applications.

During the years ended December 31, 2014 and 2013, the Company wrote off $100.1 million and $68.5 million, respectively, of property and equipment, gross, along with the associated accumulated depreciation and amortization. The write-offs were primarily related to computer and networking equipment and internal-use software no longer in use. These assets were substantially depreciated and amortized.