Summary of Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Number of shares
Number of shares, Options outstanding, beginning of year	3,561	5,001	6,663
Number of shares, Granted	470	511	746
Number of shares, Exercised	(1,293)	(1,698)	(1,190)
Number of shares, Canceled	(173)	(253)	(1,218)
Number of shares, Options outstanding, end of year	2,565	3,561	5,001
Number of shares, Options exercisable, end of year	1,828	2,078	3,013
Weighted average exercise price
Weighted average exercise price, Options outstanding, beginning of year	$ 6.53	$ 6.25	$ 6.80
Weighted average exercise price, Granted	$ 9.27	$ 8.75	$ 5.42
Weighted average exercise price, Exercised	$ 3.76	$ 5.95	$ 4.68
Weighted average exercise price, Canceled	$ 9.83	$ 9.41	$ 10.31
Weighted average exercise price, Options outstanding, end of year	$ 8.20	$ 6.53	$ 6.25
Weighted average exercise price, Options exercisable, end of year	$ 8.18	$ 7.53	$ 8.15