Segments Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segments Information
Revenue	$ 1,445,176	$ 1,279,026	$ 2,506,742	$ 2,160,661
Intersegment revenue elimination
Segments Information
Revenue	15,100	10,800	26,100	19,200
Consumer services and plans
Segments Information
Revenue	52,748	48,103	106,556	98,349
Consumer services and plans | Operating Segments
Segments Information
Revenue	52,748	48,103	106,556	98,349
Retail
Segments Information
Revenue	1,392,428	1,230,923	2,400,186	2,062,312
Retail | Operating Segments
Segments Information
Revenue	$ 1,392,428	$ 1,230,923	$ 2,400,186	$ 2,062,312