Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment per unit value, minimum	$ 1,000								$ 1,000
Property, plant and equipment, estimated useful life									1 year
Property, software and equipment depreciation, amortization expense									$ (436,300,000)	$ (402,100,000)	$ (401,200,000)
Net income	$ 113,370,000	$ 158,623,000	$ 161,915,000	$ 123,146,000	$ 119,100,000	$ 137,890,000	$ 113,915,000	$ 107,130,000	$ 557,054,000	$ 478,035,000	$ 298,373,000
Basic (in dollars per share)	$ 0.70	$ 0.97	$ 1.00	$ 0.76	$ 0.74	$ 0.85	$ 0.70	$ 0.66	$ 3.43	$ 2.94	$ 1.78
Network Assets
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in years)										5 years	4 years
Network Assets | Change In Average Useful Lives
Property, Plant and Equipment [Line Items]
Property, software and equipment depreciation, amortization expense									$ 22,900,000	$ 31,500,000
Net income									$ 19,200,000	$ 26,100,000
Basic (in dollars per share)									$ 0.12	$ 0.16