Notes Payable (Details Textual) (USD $)	12 Months Ended	1 Months Ended	12 Months Ended				12 Months Ended
	Dec. 31, 2010	Apr. 30, 2011 Senior Notes One [Member]	Dec. 31, 2012 Senior Notes One [Member]	Dec. 31, 2010 Senior Notes One [Member]	Apr. 21, 2011 Senior Notes One [Member]	Dec. 31, 2012 Unsecured revolving credit facility before amendment [Member]	Dec. 31, 2012 Unsecured revolving credit facility after amended [Member]	Dec. 31, 2011 Unsecured revolving credit facility after amended [Member]	Dec. 31, 2012 Unsecured revolving credit facility after amended [Member] Sweep service facility [Member]	Dec. 31, 2012 Letters of credit [Member]	Dec. 31, 2012 Swingline loans [Member]	Dec. 31, 2012 Maximum [Member] Senior Notes One [Member]	Dec. 31, 2012 Maximum [Member] Unsecured revolving credit facility after amended [Member]	Dec. 31, 2012 Minimum [Member] Senior Notes One [Member]	Dec. 31, 2012 Minimum [Member] Unsecured revolving credit facility after amended [Member]
Notes Payable (Textual) [Abstract]
Revolving credit facility capacity Period after amendment							5 years
Revolving credit facility before amended							Jun. 15, 2017			Jun. 15, 2017
Unsecured revolving credit facility										$ 25,000,000	$ 10,000,000
Revolving Enhanced Borrowing							450,000,000		430,000,000
Additional capacity							30,000,000
Credit facility, current										5,000,000
Credit facility, maximum						350,000,000	420,000,000		228,000,000	10,000,000
Amount outstanding									202,000,000
Consolidated Fixed Charge Coverage Ratio												2.50	2.50	1.00	1.00
Line of Credit Facility Covenants Aggregate Fixed Charge Coverage Ratio, actual												1.00	1.00	4.04	4.04
Line of credit facility covenants tangible net worth description			Permit Tangible Net Worth, calculated as of the last day of each fiscal quarter, to be less than the sum of (i) $229.0 million, plus (ii) 25% of net income for such fiscal quarter subsequent to December 31, 2010, plus (iii) 90% of the net cash proceeds from the issuance of the Company’s capital stock after December 31, 2010.				Permit 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 (as defined in the Amended Credit Facility) (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												2.75	2.75	1.00	1.00
Consolidated Leverage Ratio, actual												1.00	1.00	1.91	1.91
Tangible Net Worth sum	229,000,000		262,600,000				262,600,000	246,103,400
Consolidated Net Income				0.25				0.25
Net Cash Proceeds from the issuance of Capital Stock				0.90				0.90
Actual tangible net worth			325,600,000				325,600,000
Aggregate principal amount					$ 100,000,000
Interest Rate					4.03%
Maturity period		Apr. 21, 2018
Maturity period of interest payment due		Apr. 21, 2014
Aggregate principal amount mature		12 years
Average life		10 years