Contingently Issuable Common Stock (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended			0 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 10, 2010 Nellix	Dec. 31, 2012 Nellix
Business Acquisition [Line Items]
Purchase price of common shares				3.2
Value of common shares				$ 19,400,000
Maximum shares issuable				10.2	4.2
Fair value of contingent payment	52,400,000	38,700,000		28,200,000
Business acquisition, closing stock price					$ 14.24
Business acquisition, contingent consideration, at fair value hypothetical value					59,800,000
Business acquisition, increase (decrease) common stock					$ 2.76
Business acquisition, percentage increase (decrease)					24.00%
Fair Value of Contingently Issuable Common Stock [Roll Forward]
December 31, 2011	38,700,000
Change in fair value of contingent consideration related to acquisition	13,700,000	10,500,000	0
December 31, 2012	$ 52,400,000	$ 38,700,000		$ 28,200,000