Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Capital Stock Class B Putable [Member]	Retained Earnings	Retained Earnings, Restricted [Member]	Retained Earnings, Unrestricted [Member]	Accumulated Other Comprehensive Income [Member]
Beginning balance (shares) at Dec. 31, 2017		52
Beginning balance at Dec. 31, 2017	$ 7,267	$ 5,154	$ 2,003	$ 380	$ 1,623	$ 110
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends on capital stock	(65)
Ending balance (shares) at Mar. 31, 2018		47
Ending balance at Mar. 31, 2018	6,895	$ 4,748	2,052	403	1,649	95
Beginning balance (shares) at Dec. 31, 2017		52
Beginning balance at Dec. 31, 2017	7,267	$ 5,154	2,003	380	1,623	110
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock (shares)		61
Issuance of capital stock	6,132	$ 6,132
Repurchase/redemption of capital stock (shares)		(60)
Repurchase/redemption of capital stock	(5,953)	$ (5,953)
Net Shares Reclassified to Mandatorily Redeemable Capital Stock, Shares		0
Net shares reclassified to mandatorily redeemable capital stock	(33)	$ (33)
Comprehensive income (loss)	206		221	44	177	(15)
Cash dividends on capital stock	(145)		(145)	0	(145)
Ending balance (shares) at Jun. 30, 2018		53
Ending balance at Jun. 30, 2018	7,474	$ 5,300	2,079	424	1,655	95
Beginning balance (shares) at Mar. 31, 2018		47
Beginning balance at Mar. 31, 2018	6,895	$ 4,748	2,052	403	1,649	95
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock (shares)		26
Issuance of capital stock	2,637	$ 2,637
Repurchase/redemption of capital stock (shares)		(20)
Repurchase/redemption of capital stock	(2,084)	$ (2,084)
Net Shares Reclassified to Mandatorily Redeemable Capital Stock, Shares		0
Net shares reclassified to mandatorily redeemable capital stock	(1)	$ (1)
Comprehensive income (loss)	107		107	21	86	0
Cash dividends on capital stock	(80)		(80)	0	(80)
Ending balance (shares) at Jun. 30, 2018		53
Ending balance at Jun. 30, 2018	7,474	$ 5,300	2,079	424	1,655	95
Beginning balance (shares) at Dec. 31, 2018		55
Beginning balance at Dec. 31, 2018	7,647	$ 5,486	2,110	463	1,647	51
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends on capital stock	(85)
Ending balance (shares) at Mar. 31, 2019		48
Ending balance at Mar. 31, 2019	6,923	$ 4,753	2,126	484	1,642	44
Beginning balance (shares) at Dec. 31, 2018		55
Beginning balance at Dec. 31, 2018	7,647	$ 5,486	2,110	463	1,647	51
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock (shares)		49
Issuance of capital stock	4,931	$ 4,931
Repurchase/redemption of capital stock (shares)		(52)
Repurchase/redemption of capital stock	(5,221)	$ (5,221)
Net Shares Reclassified to Mandatorily Redeemable Capital Stock, Shares		0
Net shares reclassified to mandatorily redeemable capital stock	0	$ 0
Comprehensive income (loss)	179		194	39	155	(15)
Cash dividends on capital stock	(166)		(166)	0	(166)
Ending balance (shares) at Jun. 30, 2019		52
Ending balance at Jun. 30, 2019	7,370	$ 5,196	2,138	502	1,636	36
Beginning balance (shares) at Mar. 31, 2019		48
Beginning balance at Mar. 31, 2019	6,923	$ 4,753	2,126	484	1,642	44
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock (shares)		29
Issuance of capital stock	2,902	$ 2,902
Repurchase/redemption of capital stock (shares)		(25)
Repurchase/redemption of capital stock	(2,459)	$ (2,459)
Net Shares Reclassified to Mandatorily Redeemable Capital Stock, Shares		0
Net shares reclassified to mandatorily redeemable capital stock	0	$ 0
Comprehensive income (loss)	85		93	18	75	(8)
Cash dividends on capital stock	(81)		(81)	0	(81)
Ending balance (shares) at Jun. 30, 2019		52
Ending balance at Jun. 30, 2019	$ 7,370	$ 5,196	$ 2,138	$ 502	$ 1,636	$ 36