Stockholders' Equity - Summary of Stock Options Granted (Details) (USD $)	74 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 April 16, 2013 [Member]	Jun. 30, 2013 April 17, 2012 [Member]	Jun. 30, 2013 April 19, 2011 [Member]	Jun. 30, 2013 April 20, 2010 [Member]	Jun. 30, 2013 April 21, 2009 [Member]	Jun. 30, 2013 April 15, 2008 [Member]	Jun. 30, 2013 April 17, 2007 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	8,100,000	205,000	1,235,000	410,000	530,000	790,000	550,000	4,380,000
Option exercise (strike) price		$ 54.00	$ 54.00	$ 35.00	$ 30.00	$ 27.00	$ 27.00	$ 22.50
Closing stock price on date of grant		$ 49.25	$ 49.01	$ 31.78	$ 27.13	$ 17.61	$ 24.35	$ 20.15
Options outstanding	4,517,555	182,500	1,132,500	370,000	320,000	425,800	225,900	1,860,855
Options vested	1,496,805	0	0	0	0	180,800	124,650	1,191,355