Contingently Issuable Common Stock (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended
	Dec. 10, 2010	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Business Combinations [Abstract]
Purchase price common shares	3.2
Common shares value	$ 19,400,000
Maximum shares issuable	10.2			4.0
Fair value of contingent payment	28,200,000	57,600,000		57,600,000
closing stock price		$ 16.14		$ 16.14
Contingent consideration, at fair value hypothetical value		64,600,000		64,600,000
Business acquisition, increase (decrease) common stock				$ 1.90
Business acquisition, percentage increase (decrease)				13.30%
Fair Value of Contingently Issuable Common Stock [Roll Forward]
December 31, 2012		57,600,000		57,600,000		52,400,000
Fair value adjustment of Contingent Payment during the period		(7,600,000)	990,000	(5,200,000)	(12,700,000)
March 31, 2013	$ 28,200,000	$ 57,600,000		$ 57,600,000