Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 104,700		$ 101,400
Capitalized internal-use software, net	34,200		$ 33,400
Depreciation and amortization	39,008	$ 42,598
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation and amortization	$ 33,700	$ 35,300