XML 52 R42.htm IDEA: XBRL DOCUMENT v3.19.1
Net Income Per Share - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Dividends declared per share, in dollars per share $ 0.73 $ 0.69
Net income allocated to PRS $ 0.1 $ 0.3
Employee Stock Option    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Stock excluded from computation of diluted net income per share 0 0
Stock-Settled Appreciation Rights (SARs)    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Stock excluded from computation of diluted net income per share 0 0