Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended							12 Months Ended			15 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 subsidiary	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012
Schedule of Summary of Significant Accounting Policies [Line Items]
Number of Subsidiaries								2
Guarantee and commitment fees	$ 6,568	$ 6,401	$ 6,064	$ 5,930	$ 5,966	$ 6,320	$ 6,387	$ 24,963	$ 24,821	$ 24,091	$ 6,148
FMMSC
Schedule of Summary of Significant Accounting Policies [Line Items]
Guarantee and commitment fees								$ 10,300	$ 9,000	$ 6,500