Commitments and Contingencies - Additional Information (Detail) (USD $)
|
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2012
|
Dec. 31, 2011
|
Dec. 31, 2010
|
|
Commitments and Contingencies [Line Items] | |||
Rental expense | $ 39,810,000 | $ 34,951,000 | $ 35,216,000 |