Reconciliation of Beginning and Ending Balances of Gross Unrecognized Tax Benefits (Parenthetical) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011
Income Tax Contingency [Line Items]
Reduction of unrecognized tax benefits due to settlement	$ 41,155,000	[1]
Income taxes paid	$ 20,000,000

[1] 2011 activity represents a $41 million reduction in gross unrecognized tax benefits due to the settlement of the federal income tax audit for the years 2002 - 2005 of which $20 million represents a cash payment.