Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Income tax provision as percentage of income before taxes	4.30%
Benefit for 2012 research tax credits	$ 1,400,000
Percentage of income before taxes		33.50%
Liability for uncertain tax positions	12,100,000
Net liability, reduced for the federal effects of potential state tax exposures	8,800,000
Tax provision, included not yet reduced income tax payments	5,300,000
Anticipated significant change to uncertain income tax positions accrued in current and long term taxes payable	3,500,000
Long-term uncertain income tax positions within the next 12 months	3,273,000		2,759,000
Accrued Income Taxes, Current	270,000
Interest and penalties related to income tax	394,000			354,000
Current deferred tax assets	19,900,000
Net long-term deferred tax assets	428,000
Deferred tax valuation allowance	$ 7,900,000