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Stockholder's Equity - Additional Information (Detail) (USD $)
3 Months Ended 0 Months Ended
Mar. 31, 2015
Mar. 31, 2014
May 04, 2015
Jul. 25, 2011
Stockholders Equity [Line Items]        
Common stock, value of shares authorized to repurchase       $ 200,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
Stock repurchase, shares 0us-gaap_StockRepurchasedDuringPeriodShares 32,000us-gaap_StockRepurchasedDuringPeriodShares    
Value of shares repurchased   945,000us-gaap_StockRepurchasedDuringPeriodValue    
Average price of repurchased shares   $ 29.81us-gaap_TreasuryStockAcquiredAverageCostPerShare    
Cash dividends per common share $ 0.165us-gaap_CommonStockDividendsPerShareCashPaid $ 0.160us-gaap_CommonStockDividendsPerShareCashPaid    
Dividend payment to common shareholders $ 8,784,000us-gaap_PaymentsOfDividendsCommonStock $ 8,553,000us-gaap_PaymentsOfDividendsCommonStock    
Subsequent Event [Member]        
Stockholders Equity [Line Items]        
Dividend declared date     May 04, 2015  
Cash dividend to be paid     $ 0.17us-gaap_DividendsPayableAmountPerShare
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Dividend to be paid date     Jun. 12, 2015  
Dividend declared, shareholders of record date     Jun. 01, 2015