Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 105,300		$ 105,300		$ 101,400
Capitalized internal-use software, net	31,200		31,200		$ 33,400
Depreciation and amortization	42,584	$ 42,196	122,249	$ 128,048
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation and amortization	$ 37,400	$ 35,300	$ 106,500	$ 106,600