Summary of Activity Related to Uncertain Tax Positions (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Contingency [Line Items]
Balance at January 1	$ 1,412	$ 1,315	$ 1,342
Additions based on tax positions related to the current year	178	178	149
Additions for tax positions of prior years	83	22	18
Prior year reductions	(315)	(13)	(26)
Statute expirations	(83)	(90)	(63)
Settlements	(17)		(105)
Balance at December 31	$ 1,258	$ 1,412	$ 1,315