Commercial Mortgage Loans - Additional Information (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended
	Sep. 30, 2013 participation_interest	Mar. 31, 2013 Hotel [Member] Maryland [Member]	Sep. 30, 2013 Mixed Use [Member] Massachusetts [Member] acre		Dec. 31, 2012 Mixed Use [Member] Massachusetts [Member] acre
Mortgage Loans on Real Estate [Line Items]
Fees received on transfer of controlling ownership		$ 280
Senior Sub-Participation Interests	2
Area of property (in acres)			20	[1]	20	[1]
Sub-participation percentage of par	78.00%
Sub-participation brokerage fee	3.00%
Internal rate of return	25.00%

[1] This loan includes two one-year extension options subject to certain conditions and the payment of a fee for each extension.