Business Overview and Summary of Significant Accounting Policies - Narrative (Details)		12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)
Accounting Policies [Abstract]
Number of business segments | segment		1
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for doubtful accounts receivable, current		$ 0	$ 0
Provision for doubtful accounts		$ 0	$ 0	$ 0
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue	$ 143,400,000
Equity Securities | Unrestricted | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from accumulated other comprehensive income, current period, before tax	6,600,000
Pro Forma | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use asset					$ 30,000,000
Lease liabilities					$ 30,000,000
Three individual customers | Customer concentration risk | Gross Sales Revenue
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, percentage		99.00%	99.00%
Retained Earnings | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax	(143,400,000)
Retained Earnings | Equity Securities | Unrestricted | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax	$ 6,600,000