|
Lease Obligations - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Dec. 31, 2010
|
|
| Leases [Line Items] | |||
| Rental expense | $ 52.5 | $ 49.2 | $ 43.5 |