Balance Sheet Offsetting (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Securities Borrowed:
Gross Amounts of Recognized Assets	$ 100,348	$ 103,936
Net Amounts of Assets Presented in the Balance Sheets	100,348	103,936
Gross Amounts Not Offset in the Balance Sheets
Financial Instruments	(100,348)	(103,936)
Institutional Counterparties
Securities Borrowed:
Gross Amounts of Recognized Assets	100,348	103,936
Net Amounts of Assets Presented in the Balance Sheets	100,348	103,936
Gross Amounts Not Offset in the Balance Sheets
Financial Instruments	$ (100,348)	$ (103,936)