PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT

Property and equipment at December 31, 2017 and 2016 consisted of the following (in thousands):

	2017			2016			Estimated Useful Lives (years)
Computer equipment and software	$	769,622		$	522,675		1 to 5 years
Leasehold improvements	198,766			143,191			1 to 15 years
Office equipment, furniture and fixtures	46,722			34,176			3 to 10 years
Building construction-in-progress	8,388			5,945
Total	1,023,498			705,987
Less: accumulated depreciation	(543,417		)	(358,970		)
Property and equipment, net	$	480,081		$	347,017

Depreciation expense was approximately $187.2 million, $140.1 million and $101.5 million for the years ended December 31, 2017, 2016 and 2015, respectively.