Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 100,400		$ 100,400		$ 92,700
Capitalized internal-use software, net	35,300		35,300		$ 33,600
Depreciation and amortization	42,196	$ 41,747	128,048	$ 111,996
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation and amortization	$ 35,300	$ 35,200	$ 106,600	$ 95,000