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Restricted Stock, Performance Share and Cash Awards - Schedule of Restricted Stock Awards Vesting Periods (Detail) - shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Vesting Period [Line Items]      
Shares granted in the period 394,975 376,541 369,975
Vesting Period One Year [Member]      
Vesting Period [Line Items]      
Shares granted in the period 22,175 19,250 19,375
Vesting period, years 1 year    
Vesting Period Three Years [Member]      
Vesting Period [Line Items]      
Shares granted in the period   33,741  
Vesting period, years 3 years    
Vesting Period Four Years [Member]      
Vesting Period [Line Items]      
Shares granted in the period 9,200 323,550 345,000
Vesting period, years 4 years    
Vesting Period Five Years [Member]      
Vesting Period [Line Items]      
Shares granted in the period 363,600   5,600
Vesting period, years 5 years