Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Additional Information (Detail)

v2.4.0.6
Share-Based Compensation - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Share-based compensation expense $ 3.3 $ 3.6 $ 10.0 $ 10.8
Unrecognized compensation cost related to nonvested $ 1.4   $ 1.4  
Unrecognized compensation cost weighted average amortization period     10 months 24 days