Annual report pursuant to Section 13 and 15(d)

Summary of Potential Number of Shares Vesting under Restricted Stock (Detail)

v2.4.0.6
Summary of Potential Number of Shares Vesting under Restricted Stock (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
at IRR of at least 8.5%
      
Schedule Of Stock Options [Line Items]      
Number of shares vesting at IRR level of at least 8.5% 50,981 51,239 132,144
Fair value of shares vesting at IRR level of at least 8.5% $ 1,103 $ 991 $ 2,423
at IRR of at least 10.5%
      
Schedule Of Stock Options [Line Items]      
Number of shares vesting at IRR level of at least 10.5% 101,974 102,488 264,288
Fair value of shares vesting at IRR level of at least 10.5% 2,206 1,983 4,847
at IRR of at least 12.5%
      
Schedule Of Stock Options [Line Items]      
Number of shares vesting at IRR level of at least 12.5% 152,955 153,727 396,429
Fair value of shares vesting at IRR level of at least 12.5% $ 3,308 $ 2,975 $ 7,271