Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Unrecognized Tax Benefits
Balance at beginning of year	$ 45,049	$ 44,722
Additions based on tax positions related to the current year	4,185	3,291
Reductions for tax positions of prior years	(8,928)	(2,964)
Settlements	(62)
Balance at end of year	$ 40,244	$ 45,049