Reconciliation of Beginning and Ending Amount 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 [Line Items]
Balance at beginning of year	$ 323	$ 214
Additions based on tax positions related to the current year	108	108
Additions for tax positions of prior year	0	1
Reductions for tax positions of prior years	0	0
Settlements	0	0
Balance at end of year	$ 431	$ 323