Notes Payable (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended				12 Months Ended		0 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Oct. 04, 2011 Bank Of America [Member]	Oct. 04, 2011 Union Bank [Member]	Dec. 31, 2012 Union Bank [Member]	Dec. 31, 2011 Union Bank [Member]	Dec. 31, 2011 Senior Notes [Member]	Dec. 31, 2012 Senior Notes [Member]	Aug. 04, 2011 AIS [Member]	Dec. 31, 2012 AIS [Member]	Dec. 31, 2011 AIS [Member]	Dec. 31, 2009 AIS [Member] Minimum [Member]	Dec. 31, 2009 AIS [Member] Maximum [Member]
Debt Instrument [Line Items]
Loan maximum borrowing capacity				$ 18,000,000		$ 20,000,000	$ 20,000,000				$ 120,000,000	$ 120,000,000
Advance rate used to calculate collateral requirement													75.00%	100.00%
Credit facility maturity date range, start										Jan. 01, 2012
Credit facility maturity date range, end										Jan. 02, 2015
Basis spread on variable rate				0.50%	0.40%					0.40%
Loan expiration date				Mar. 01, 2013	Jan. 02, 2015
Senior notes retired	0	125,000,000	0					125,000,000
Unsecured senior notes interest rate								7.25%
Notes maturity date								Aug. 15, 2011
Note payable at maturity date	$ 140,000,000	$ 140,000,000							$ 140,000,000