Stockholders' Equity - Registered Offering (Details) - Common stock - Goldman Sachs & Co. LLC - Underwriting Agreement - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Registered Offering
Stockholders' Equity
Number of shares sold by the entity	1,079,580	1,731,929
Number of days granted to purchase additional shares	30 days	30 days
Issue price of stock	$ 305.00	$ 83.00
Net proceeds after deducting commissions and other transactions costs	$ 311.8	$ 135.5
Additional Shares
Stockholders' Equity
Number of shares sold by the entity	95,973	225,904

Number of new stock issued during the period.

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