Stockholders' Equity (Narrative) (Details) (USD $)	1 Months Ended		1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	Apr. 30, 2012	Sep. 30, 2012 Series A Common Stock [Member]	Apr. 30, 2012 Quarterly [Member]	Mar. 31, 2012 Quarterly [Member]	Apr. 30, 2012 Annual [Member]	Mar. 31, 2012 Annual [Member]	Sep. 30, 2012 Senior Unsecured Notes Due 2018 [Member]	Dec. 31, 2011 Senior Unsecured Notes Due 2018 [Member]	Sep. 30, 2010 Senior Unsecured Notes Due 2018 [Member]	Sep. 30, 2012 Senior Unsecured Notes Due 2021 [Member]	Dec. 31, 2011 Senior Unsecured Notes Due 2021 [Member]	May 31, 2011 Senior Unsecured Notes Due 2021 [Member]
Class of Stock [Line Items]
Common stock, par value		$ 0.0001
Interest rate, stated percentage							6.625%	6.625%	6.625%	5.875%	5.875%	5.875%
Common stock, dividends, rate increase, percent	25.00%
Common stock, dividends, per share, declared			$ 0.075	$ 0.06	$ 0.30	$ 0.24