Subsequent Events - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended		1 Months Ended
	Dec. 31, 2013 Restricted stock based compensation	Dec. 31, 2012 Restricted stock based compensation	Feb. 20, 2014 Dividend Declared	Feb. 27, 2014 Performance Shares Issued To Officers Restricted stock based compensation	Feb. 27, 2014 Performance Shares Issued To Officers Restricted stock based compensation Other Employees	Feb. 27, 2014 Performance Shares Issued To Officers Restricted Stock Units (RSUs) Officers and executive officers
Subsequent Event [Line Items]
Number of shares issued	423,000	349,000		500,000	200,000	300,000
Aggregate value of shares issued				$ 16.9
Vesting period						3 years
Percent of awards eligible to vest						33.33%
Performance criteria, cumulative period						3 years
Dividend declared per common share			$ 0.51
Dividend payable date			Apr. 15, 2014
Dividend declared, record date			Apr. 02, 2014