Income Taxes (Details 3)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Disclosure - Income Taxes - Additional Information [Abstract]
Statutory federal tax rate	35.00%	35.00%	35.00%
Foreign rate differential	(10.40%)	(3.80%)	(1.90%)
Foreign, federal and state income tax credits	(2.70%)	(2.90%)	(1.50%)
State taxes	0.30%	2.20%	2.60%
Non-deductible expenses	0.70%	(1.20%)	(1.60%)
Other	(0.10%)	(0.90%)	(1.10%)
Effective tax rate	22.80%	28.40%	31.50%