Net Income Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Sep. 17, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Dividends declared per share, in dollars per share		$ 0.75	$ 0.73	$ 1.50	$ 1.46
Tangible equity units issued	16,500,000
Tangible equity units proceeds	$ 800.2
Price for basic share (usd per share)				0.3134	0.3134
Tangible Equity Units, Price for Shares Diluted	$ 0.3839			$ 0.3839	$ 0.3408
Net income allocated to PRS		$ 0.1	$ 0.2	$ 0.3	$ 0.3