Borrowed Funds (Details 2) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011 Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2012 [Member] Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 2012 [Member] Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2013 [Member] Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2014 [Member] Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2015 [Member] Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 2015 [Member] Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2016 [Member] Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 2016 [Member] Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2017 [Member] Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 2018 [Member] Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 2018 [Member] Borrowings by Earlier of Scheduled Maturity or Next Potential Put Date [Member]	Mar. 31, 2011 2019 [Member] Borrowings by Scheduled Maturity Date [Member]	Mar. 31, 2011 2020 [Member] Borrowings by Scheduled Maturity Date [Member]
Borrowed funds maturities and potential put dates
Borrowed funds	$ 14,175,000	$ 15,075,000	$ 14,175,000	$ 14,175,000	$ 2,000,000	$ 4,675,000	$ 1,325,000	$ 3,725,000	$ 75,000	$ 275,000	$ 3,925,000	$ 3,925,000	$ 2,475,000	$ 700,000	$ 250,000	$ 1,725,000	$ 3,275,000
Weighted Average Rate			4.06%	4.06%	0.84%	2.88%	4.69%	4.47%	4.62%	4.10%	4.92%	4.92%	4.37%	3.65%	3.10%	4.62%	4.53%