Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Apr. 16, 2018	Apr. 30, 2018
Subsequent Event [Line Items]
Common stock shares issued		30,262,250
Common stock offering price to public		$ 47.50
Proceeds from common stock issuance, net		$ 1,400.0
DST [Member]
Subsequent Event [Line Items]
Business acquisition, effective date of acquisition	Apr. 16, 2018
Purchase of outstanding stock of DST Systems, Inc. in cash, including assumption of debt, plus costs, fees and expenses	$ 5,000.0
Senior Secured Credit Facilities [Member] | DST [Member]
Subsequent Event [Line Items]
Amount borrowed in connection with acquisition	7,400.0
Amount rolled over from existing credit facility	524.5
Senior Secured Credit Facilities Revolving Portion [Member] | DST [Member]
Subsequent Event [Line Items]
Undrawn revolver	$ 250.0