Notes Payable (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Information relates to the lines of credit
Maximum amount outstanding	$ 220,799	$ 262,461
Average amount outstanding	$ 206,514	$ 206,227
Weighted average interest rate, during the period	2.51%	2.22%
Weighted average interest rate, end of period	1.71%	1.79%
Prime interest rate, end of period	3.25%	3.25%