Equity (Details) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	May 25, 2017 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) shares	Mar. 26, 2018 shares	Jun. 30, 2018 USD ($) shares	May 10, 2018 USD ($)	Dec. 31, 2017 shares	Dec. 14, 2017 USD ($)
Initial Public Offering
Conversion ratio of stock-split	66,498.762
Common Stock
Share buybacks | shares		1,026,000		5,651,037
Income tax withholding | shares		296,133		307,765
Number of shares purchased (in shares) | shares		1,322,133	5,100,000	5,958,802
Common stock shares repurchased | shares		6,419,975		6,419,975		461,173
Purchase of shares | $		$ 9.6		$ 57.7
IPO
Initial Public Offering
Shares issued | shares	20,970,589
Share price (in dollars per share) | $ / shares	$ 17
Gross proceeds | $	$ 356.5
Issuance costs | $	22.5
Proceeds from issuance of common stock, net of issuance costs | $	$ 334.0
Maximum
Common Stock
Common stock repurchase authorized amount | $					$ 25.0		$ 50.0