Regulatory Restrictions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2009
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Assets	$ 35,879,416	$ 32,548,069		$ 15,000,000
Mortgage finance(1)	7,588,803	8,169,849
Mortgage Finance, Average Balance	7,100,000
Common Equity Tier 1 [Abstract]
CET1, actual amount	2,646,323	2,653,999
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets), actual amount	3,415,854	3,398,345
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets), actual amount	2,901,225	2,912,529
Tier 1 capital (to average assets):
Tier 1 capital (to average assets), actual amount	$ 2,901,225	$ 2,912,529
Risk Based Ratios [Abstract]
CET1, actual ratio	9.27%	8.88%
Total capital (to risk weighted assets), actual ratio	11.96%	11.37%
Tier 1 capital (to risk-weighted assets), actual ratio	10.16%	9.75%
Tier 1 capital (to average assets), actual ratio	8.48%	8.42%
Bank
Common Equity Tier 1 [Abstract]
CET1, actual amount	$ 2,673,198	$ 2,676,513
CET1 to be well capitalized under prompt corrective action provisions, amount	1,853,888	1,941,522
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets), actual amount	3,283,989	3,262,144
Total capital (to risk weighted assets) to be well capitalized under prompt corrective action provisions, amount	2,852,135	2,986,957
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets), actual amount	2,828,100	2,835,043
Tier 1 capital (to risk weighted assets) to be well capitalized under prompt corrective action provisions, amount	2,281,708	2,389,565
Tier 1 capital (to average assets):
Tier 1 capital (to average assets), actual amount	2,828,100	2,835,043
Tier 1 capital (to average assets) to be well capitalized under prompt corrective action provisions, amount	$ 1,710,181	$ 1,728,988
Risk Based Ratios [Abstract]
CET1, actual ratio	9.37%	8.96%
CET1 to be well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Total capital (to risk weighted assets), actual ratio	11.51%	10.92%
Total capital (to risk weighted assets) to be well capitalized under prompt corrective action provisions, ratio	10.00%	10.00%
Tier 1 capital (to risk-weighted assets), actual ratio	9.92%	9.49%
Tier 1 capital (to risk weighted assets) to be well capitalized under prompt corrective action provisions, ratio	8.00%	8.00%
Tier 1 capital (to average assets), actual ratio	8.27%	8.20%
Tier 1 capital (to average assets) to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Basel III, Phased-In
Common Equity Tier 1 [Abstract]
CET1 for capital adequacy purposes, amount	$ 1,998,473	$ 2,091,591
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets) for capital adequacy purposes, amount	2,997,710	3,137,926
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, amount	2,426,717	2,540,226
Tier 1 capital (to average assets):
Tier 1 capital (to average assets) for capital adequacy purposes, amount	$ 1,368,689	$ 1,383,640
Risk Based Ratios [Abstract]
CET1 for capital adequacy purposes, ratio	7.00%	7.00%
Total capital (to risk weighted assets) for capital adequacy purposes, ratio	10.50%	10.50%
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, ratio	8.50%	8.50%
Tier 1 capital (to average assets) for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 capital (to average assets) to be well capitalized under prompt corrective action provisions, ratio			2.50%
Basel III, Phased-In | Bank
Common Equity Tier 1 [Abstract]
CET1 for capital adequacy purposes, amount	$ 1,996,495	$ 2,090,870
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets) for capital adequacy purposes, amount	2,994,742	3,136,305
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, amount	2,424,315	2,538,913
Tier 1 capital (to average assets):
Tier 1 capital (to average assets) for capital adequacy purposes, amount	$ 1,368,145	$ 1,383,190
Risk Based Ratios [Abstract]
CET1 for capital adequacy purposes, ratio	7.00%	7.00%
Total capital (to risk weighted assets) for capital adequacy purposes, ratio	10.50%	10.50%
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, ratio	8.50%	8.50%
Tier 1 capital (to average assets) for capital adequacy purposes, ratio	4.00%	4.00%