XML 18 R112.htm IDEA: XBRL DOCUMENT v2.4.0.8
Benefit Plans - Summary of Fair Values for Stock-based Awards Granted Using Black-Scholes Option Pricing Model (Detail) (Black-Scholes Option Pricing Model [Member], USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted-average fair value of grants $ 5.31 $ 5.07 $ 5.63
Risk-free interest rate (range), minimum 0.90% 0.50% 1.40%
Risk-free interest rate (range), maximum 1.80% 1.10% 3.00%
Expected life (range)     7 years
Expected volatility (range), minimum 49.20% 50.80% 52.10%
Expected volatility (range), maximum 52.50% 66.80% 69.00%
Minimum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield (range) 4.10% 3.60% 3.40%
Expected life (range) 5 years 4 years  
Maximum [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Dividend yield (range) 4.50% 4.70% 4.90%
Expected life (range) 6 years 5 years