Common Stock and Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
0 Months Ended 1 Months Ended 12 Months Ended
Aug. 13, 2013
Feb. 28, 2013
Dec. 31, 2013
Dec. 31, 2012
Jun. 09, 2009
Equity [Abstract]          
Common shares, Authorized     75,000,000 75,000,000 75,000,000
Preferred stock, Authorized     5,000,000 5,000,000 5,000,000
Share repurchase program $ 50 $ 25      
Number of shares repurchased     1,268,643    
Average price of repurchased shares     $ 24.06    
Total cost of shares repurchased     30.5    
Amount available under repurchase program     $ 35.9