Income Taxes (Details 3)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Disclosure - Income Taxes - Additional Information [Abstract]
Statutory federal tax rate	35.00%	35.00%	35.00%
Foreign rate differential	(3.80%)	(1.90%)	(4.00%)
Federal and state income tax credits	(2.90%)	(1.50%)	(4.70%)
State taxes	2.20%	2.60%	2.60%
Non-deductible expenses	(1.20%)	(1.60%)	3.00%
Other	(0.90%)	(1.10%)	0.50%
Effective tax rate	28.40%	31.50%	32.40%