Summary of Significant Accounting Policies - Intangible Assets (Details) (USD $)	1 Months Ended	12 Months Ended
	Apr. 30, 2007	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 22, 2006
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible asset, amount					$ 33,000,000
Finite-lived intangible asset, useful life		6 years 9 months
Finite-lived intangible assets, purchase accounting adjustments	1,000,000
Amortization expense		$ 0	$ 0	$ 2,522,364