Statements of Capital (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 1,770,634	$ 1,704,835
Proceeds from sale of capital stock			716,886	535,053
Repurchase/redemption of capital stock			(770,885)	(544,197)
Net shares reclassified to mandatorily redeemable capital stock			(25,882)	(1,632)
Comprehensive income
Net income	29,532	17,756	69,733	64,531
Other Comprehensive Income (Loss)	(3,789)	13,247	(19,412)	14,084
Dividends on capital stock (at 0.375 percent annualized rate)
Cash			(130)	(135)
Mandatorily redeemable capital stock			(24)	(16)
Ending balance	1,740,920	1,772,523	1,740,920	1,772,523
Capital Stock Class B - Putable, Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, shares			12,170	12,557
Proceeds from sale of capital stock, shares			7,169	5,351
Repurchase/redemption of capital stock, shares			(7,709)	(5,442)
Net shares reclassified to mandatorily redeemable capital stock, shares			(259)	(16)
Dividends on capital stock (at 0.375 percent annualized rate)
Stock, shares			31	33
Ending balance, shares	11,402	12,483	11,402	12,483
Capital Stock Class B - Putable, Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			1,216,986	1,255,793
Proceeds from sale of capital stock			716,886	535,053
Repurchase/redemption of capital stock			(770,885)	(544,197)
Net shares reclassified to mandatorily redeemable capital stock			(25,882)	(1,632)
Dividends on capital stock (at 0.375 percent annualized rate)
Stock			3,066	3,262
Ending balance	1,140,171	1,248,279	1,140,171	1,248,279
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			571,893	494,657
Comprehensive income
Net income			69,733	64,531
Dividends on capital stock (at 0.375 percent annualized rate)
Cash			(130)	(135)
Mandatorily redeemable capital stock			(24)	(16)
Stock			(3,066)	(3,262)
Ending balance	638,406	555,775	638,406	555,775
Retained Earnings, Restricted
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			22,276	5,918
Comprehensive income
Net income			13,947	12,906
Dividends on capital stock (at 0.375 percent annualized rate)
Ending balance	36,223	18,824	36,223	18,824
Retained Earnings, Unrestricted
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			549,617	488,739
Comprehensive income
Net income			55,786	51,625
Dividends on capital stock (at 0.375 percent annualized rate)
Cash			(130)	(135)
Mandatorily redeemable capital stock			(24)	(16)
Stock			(3,066)	(3,262)
Ending balance	602,183	536,951	602,183	536,951
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(18,245)	(45,615)
Comprehensive income
Other Comprehensive Income (Loss)			(19,412)	14,084
Dividends on capital stock (at 0.375 percent annualized rate)
Ending balance	$ (37,657)	$ (31,531)	$ (37,657)	$ (31,531)