Property and Equipment, Net (Narrative) (Details) - USD ($) $ in Thousands			3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Property and Equipment [Line Items]
Capitalized internal-use software, gross	$ 144,800	$ 138,200	$ 144,800
Capitalized internal-use software, net	34,800	31,500	34,800
Depreciation			53,089	$ 54,226
Accrued capital expenditures	$ 10,700	$ 5,200
Property and Equipment [Member]
Property and Equipment [Line Items]
Depreciation			$ 53,100	$ 54,200