Deposits Deposits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Deposits [Abstract]
Weighted Average Rate Interest Bearing Deposits	0.03%	0.03%
Interest bearing, demand and overnight	$ 932,054		$ 1,014,399
Interest bearing, term	126,200		118,425
Interest bearing, other	25,472		25,428
Total interest-bearing	1,083,726		1,158,252
Non-interest bearing, other	17,844		18,353
Total non-interest bearing	17,844		18,353
Total deposits	1,101,570		1,176,605
Time Deposits, $100,000 or More	$ 126,100		$ 118,350