Stockholders' Equity (Details 3) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Equity Incentive Plans [Member]
Valuation of options granted under the equity incentive plans and shares subject to purchase under the employees stock purchase plan
Average risk-free interest rate	0.62%	1.11%	0.87%	1.29%
Expected dividend yield	1.70%		1.70%
Expected life	4 years 6 months	3 years 6 months	4 years 6 months	3 years 6 months
Expected volatility	40.00%	40.00%	40.00%	40.00%
Weighted average fair value	$ 9.42	$ 10.01	$ 9.81	$ 10.53
Employee Stock Purchase Plan [Member]
Valuation of options granted under the equity incentive plans and shares subject to purchase under the employees stock purchase plan
Average risk-free interest rate	0.14%	0.08%	0.14%	0.14%
Expected dividend yield	1.70%		1.70%
Expected life	6 months	6 months	6 months	6 months
Expected volatility	31.00%	28.00%	31.00%	28.00%
Weighted average fair value	$ 6.89	$ 7.56	$ 6.87	$ 7.55