Business Overview and Summary of Significant Accounting Policies - Additional Information (Details) location in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) location	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Accounting Policies [Abstract]
Approximate number of in-market locations | location	3
Impairment of property and equipment long-lived assets	$ 0	$ 0	$ 0
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits from stock-based compensation	1,800,000
Reclassification offsetting cash flows used in financing activities	407,200,000	346,800,000	340,900,000
Reclassification to cash flows provided by operating activities	$ 585,200,000	519,900,000	550,300,000
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification offsetting cash flows used in financing activities		5,900,000	3,400,000
Reclassification to cash flows provided by operating activities		$ 5,900,000	$ 3,400,000