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Subsequent Event - Additional Information (Detail) - $ / shares
3 Months Ended 12 Months Ended
Feb. 01, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Subsequent Event [Line Items]                        
Dividends declared per common share (in USD per share)   $ 0.38 $ 0.38 $ 0.38 $ 0.38 $ 0.38 $ 0.38 $ 0.38 $ 0.38 $ 1.52 $ 1.52 $ 1.44
Subsequent Event                        
Subsequent Event [Line Items]                        
Dividend declared date Feb. 01, 2016                      
Dividends declared per common share (in USD per share) $ 0.38                      
Date to be paid Mar. 04, 2016                      
Date of record Feb. 17, 2016