Summary of Significant Accounting Policies Change in Accounting Principle (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Mortgage loans held for portfolio, net	$ 9,447,220		$ 9,447,220		$ 9,148,718
Total assets	109,052,805		109,052,805		104,635,281
Affordable Housing Program payable	107,321		107,321		104,883
Total liabilities	103,954,922		103,954,922		99,657,186
Retained Earnings, Unrestricted	599,926		599,926		574,122
Retained Earnings, Appropriated	290,644		290,644		260,285
Total retained earnings	890,570		890,570		834,407
Total capital	5,097,883	$ 4,983,005	5,097,883	$ 4,983,005	4,978,095	$ 5,153,125
Total liabilities and capital	109,052,805		109,052,805		$ 104,635,281
Interest income - mortgage loans held for portfolio	74,279	64,008	146,716	131,892
Net interest income	105,768	82,610	209,041	171,455
Income before assessments	96,284	68,329	168,778	131,235
Affordable Housing Program assessments	9,690	6,936	16,986	13,333
Net income	86,594	61,393	151,792	117,902
Comprehensive Income	$ 87,112	61,944	152,626	119,069
Depreciation, Amortization and Accretion, Net			24,521	28,583
Increase (Decrease) in Other Operating Liabilities			2,234	3,940
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities			70,770	40,791
Net Cash Provided by (Used in) Operating Activities, Continuing Operations			$ 222,562	158,693
Change in Amortization and Accretion Method [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Mortgage loans held for portfolio, net		8,496,646		8,496,646
Total assets		106,128,268		106,128,268
Affordable Housing Program payable		101,065		101,065
Total liabilities		101,145,263		101,145,263
Retained Earnings, Unrestricted		538,351		538,351
Retained Earnings, Appropriated		230,228		230,228
Total retained earnings		768,579		768,579		737,646
Total capital		4,983,005		4,983,005
Total liabilities and capital		106,128,268		106,128,268
Interest income - mortgage loans held for portfolio		64,008		131,892
Net interest income		82,610		171,455
Income before assessments		68,329		131,235
Affordable Housing Program assessments		6,936		13,333
Net income		61,393		117,902
Comprehensive Income		61,944		119,069
Depreciation, Amortization and Accretion, Net				28,583
Increase (Decrease) in Other Operating Liabilities				3,940
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities				40,791
Net Cash Provided by (Used in) Operating Activities, Continuing Operations				158,693
Change in Amortization and Accretion Method [Member] | Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Mortgage loans held for portfolio, net		8,509,933		8,509,933
Total assets		106,141,555		106,141,555
Affordable Housing Program payable		99,600		99,600
Total liabilities		101,143,798		101,143,798
Retained Earnings, Unrestricted		552,949		552,949
Retained Earnings, Appropriated		230,382		230,382
Total retained earnings		783,331		783,331		765,577
Total capital		4,997,757		4,997,757
Total liabilities and capital		106,141,555		106,141,555
Interest income - mortgage loans held for portfolio		58,433		117,248
Net interest income		77,035		156,811
Income before assessments		62,754		116,591
Affordable Housing Program assessments		6,378		11,868
Net income		56,376		104,723
Comprehensive Income		56,927		105,890
Depreciation, Amortization and Accretion, Net				43,227
Increase (Decrease) in Other Operating Liabilities				2,475
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities				53,970
Net Cash Provided by (Used in) Operating Activities, Continuing Operations				158,693
Change in Amortization and Accretion Method [Member] | Restatement Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Mortgage loans held for portfolio, net		(13,287)		(13,287)
Total assets		(13,287)		(13,287)
Affordable Housing Program payable		1,465		1,465
Total liabilities		1,465		1,465
Retained Earnings, Unrestricted		(14,598)		(14,598)
Retained Earnings, Appropriated		(154)		(154)
Total retained earnings		(14,752)		(14,752)		$ (27,931)
Total capital		(14,752)		(14,752)
Total liabilities and capital		(13,287)		(13,287)
Interest income - mortgage loans held for portfolio		5,575		14,644
Net interest income		5,575		14,644
Income before assessments		5,575		14,644
Affordable Housing Program assessments		558		1,465
Change in Accounting Principle, Effect of Change on Net Income		5,017		13,179
Comprehensive Income		$ 5,017		13,179
Depreciation, Amortization and Accretion, Net				(14,644)
Increase (Decrease) in Other Operating Liabilities				1,465
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities				(13,179)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations				$ 0