Business Overview and Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) location	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Approximate number of in-market locations | location	3,100
Impairment of property and equipment long-lived assets	$ 0	$ 0	$ 0
Accounting Standards Update 2016-02 | Pro Forma
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Approximate increase in assets upon adoption of ASU 2016-02, Leases	250,000,000
Approximate increase in liabilities upon adoption of ASU 2016-02, Leases	$ 250,000,000