Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) Vote	Dec. 31, 2018 USD ($) Vote	Dec. 31, 2017 USD ($)	Feb. 01, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2016 USD ($)
Acquired Indefinite-lived Intangible Assets [Line Items]
Advertising expense	$ 27,000,000.0	$ 10,600,000	$ 4,900,000
Allowance for doubtful accounts	6,287,000	4,945,000	1,033,000			$ 1,076,000
Issuance costs	953,000
Operating lease assets	156,741,000				$ 123,500,000
Operating lease, liability	166,356,000				132,000,000.0
Deferred rent credit					$ 9,000,000.0
Goodwill, impairment loss	0	0	0
Impairment of long-lived assets	0	$ 0	$ 0
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Acquired Indefinite-lived Intangible Assets [Line Items]
Operating right of use asset	33,742,000			$ 33,700,000
Operating lease liability	32,568,000			32,600,000
Finance right-of-use assets				14,200,000
Finance lease liability	$ 13,616,000			$ 13,600,000
Common Class A
Acquired Indefinite-lived Intangible Assets [Line Items]
Votes per share | Vote	1	1
Common Class B
Acquired Indefinite-lived Intangible Assets [Line Items]
Votes per share | Vote	10	10
Conversion ratio	1