Notes Payable (Details) (USD $)	9 Months Ended
	Sep. 30, 2012
Unsecured revolving credit facility before amendment [Member]
Notes Payable (Textual) [Abstract]
Unsecured revolving credit facility	$ 350,000,000
Unsecured revolving credit facility after amended [Member]
Notes Payable (Textual) [Abstract]
Revolving credit facility before amended	Jun. 15, 2017
Unsecured revolving credit facility	420,000,000
Line of Credit Facility Covenants Tangible Net Worth Description	Tangible Net Worth as of the end of any fiscal quarter of the Company to be less than the sum of (i) $246,103,400 plus (ii) 25% of the Company’s Consolidated Net Income (but only if a positive number) for each fiscal quarter ended subsequent to December 31, 2011 plus (iii) 90% of the net cash proceeds from the issuance of the Company’s capital stock after December 31, 2011.
Consolidated Leverage Ratio, Years	4 years
Tangible Net Worth sum	246,103,400
Consolidated Net Income	0.25
Net Cash Proceeds from the issuance of Capital Stock	0.90
Revolving credit facility capacity Period after amendment	5 years
Revolving Enhanced Borrowing	450,000,000
Additional commitments	30,000,000
Letters of credit [Member]
Notes Payable (Textual) [Abstract]
Revolving credit facility before amended	Jun. 15, 2017
Unsecured revolving credit facility	25,000,000
Credit facility, current	5,000,000
Credit facility, maximum	10,000,000
Swingline loans [Member]
Notes Payable (Textual) [Abstract]
Unsecured revolving credit facility	$ 10,000,000
Maximum [Member] | Unsecured revolving credit facility after amended [Member]
Notes Payable (Textual) [Abstract]
Consolidated Fixed Charge Coverage Ratio	2.50
Consolidated Leverage Ratio	2.75
Minimum [Member] | Unsecured revolving credit facility after amended [Member]
Notes Payable (Textual) [Abstract]
Consolidated Fixed Charge Coverage Ratio	1.00
Consolidated Leverage Ratio	1.00