Property and Equipment - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, software and equipment depreciation, amortization expense	$ 215,300,000	$ 162,900,000	$ 183,200,000
Capitalization of stock-based compensation	15,226,000	12,325,000	9,276,000
Impairment of long-lived assets held-for-use	100,100,000	68,500,000
Internal-use software
Property, Plant and Equipment [Line Items]
Capitalization of stock-based compensation	$ 15,200,000	$ 12,300,000	$ 9,300,000