Contingently Issuable Common Stock (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended
	Dec. 10, 2010	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Business Combinations [Abstract]
Purchase price common shares	3.2
Common shares value	$ 19,400,000
Maximum shares issuable	10.2	4.1
Fair value of contingent payment	28,200,000	57,600,000
closing stock price		$ 16.15
Contingent consideration, at fair value hypothetical value		66,200,000
Business acquisition, increase (decrease) common stock		$ 1.91
Business acquisition, percentage increase (decrease)		13.00%
Fair Value of Contingently Issuable Common Stock [Roll Forward]
December 31, 2012		57,600,000		52,400,000
Fair value adjustment of Contingent Payment during the period		5,200,000	12,450,000
March 31, 2013	$ 28,200,000	$ 57,600,000