Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 103,400		$ 103,400		$ 101,400
Capitalized internal-use software, net	31,800		31,800		$ 33,400
Depreciation and amortization	40,657	$ 43,254	79,664	$ 85,852
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation and amortization	$ 35,400	$ 36,000	$ 69,100	$ 71,300