Annual report pursuant to Section 13 and 15(d)

Stock Compensation - Additional Information (Detail)

v2.4.0.8
Stock Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Apr. 16, 2007
Jul. 01, 1998
Apr. 16, 2007
Employee Stock Purchase Plan 1998 [Member]
Jul. 01, 1998
Employee Stock Purchase Plan 1998 [Member]
Dec. 31, 2013
CLASS A COMMON STOCK [Member]
Dec. 31, 2012
CLASS A COMMON STOCK [Member]
Dec. 31, 2011
CLASS A COMMON STOCK [Member]
May 31, 2003
CLASS A COMMON STOCK [Member]
Jun. 30, 2001
CLASS A COMMON STOCK [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Number of shares authorized for issuance                     11,215,154 8,215,154
Vesting period stock option awards 3 years                      
Expiration period of stock option awards 10 years                      
Number of shares reserved for issuance       7,500,000   3,000,000 2,781,415          
Intrinsic value of options exercised $ 0.9 $ 1.9 $ 1.2                  
Stock options granted 0 0 0                  
Unrecognized compensation cost related to stock option 0 0                    
Number of shares remain available for grant 4,801,381                      
Recognized compensation expense 2.4 11.5 14.3                  
Income tax benefits (expense) 0.5 0.5 (0.6)                  
Unrecognized compensation cost related to nonvested stock 5.0 4.7                    
Weighted average period for recognition of cost 2 years 8 months 12 days 3 years 8 months 12 days                    
Total fair value of shares vested 1.4 13.1                    
Period utilized to implement employee stock purchase plan 6 months                      
Interval for purchases occurring 6 months                      
Eligibility to participate stock purchase plan At least 20 hours per week and more than five months in any calendar year.                      
Maximum percentage of employee's compensation to purchase common stock       15.00% 15.00%              
Percentage of price of common stock purchased       85.00% 85.00%              
Proceeds from issuance of common stock under the employee stock purchase plan, Shares 149,257 186,199 178,189         149,000 186,000 178,000    
Proceeds from issuance of common stock under the employee stock purchase plan $ 2.6 $ 2.4 $ 2.0