Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 107,800	$ 101,400
Capitalized internal-use software, net	30,900	33,400
Depreciation and amortization	164,915	169,662	$ 154,452
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation and amortization	$ 143,600	$ 141,300	$ 129,400