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Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Schedule Of Equity [Line Items]      
Repurchase of Company stock for retirement   $ 24,811,000  
Cash Dividend on Common Stock $ 3.20 $ 3.00 $ 2.70
Aggregated Dividend Paid $ 163,700,000 $ 153,000,000 $ 138,400,000
Minimum percentage of adjusted funds from operations as cash dividend 50.00%    
Percentage of REIT taxable income as cash dividend 100.00%    
2015 Stock Repurchase Program [Member]      
Schedule Of Equity [Line Items]      
Authorized amount for share repurchase program   $ 100,000,000  
Company repurchased, shares   0.5  
Repurchase of Company stock for retirement   $ 24,800,000