Regulatory Restrictions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Regulatory Capital Requirements [Abstract]
Required reserve balance at the Federal Reserve	$ 283,400	$ 157,700
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Mortgage finance(1)	8,169,849	5,877,524
Mortgage Finance, Average Balance	7,900,000
Common Equity Tier 1 [Abstract]
CET1, actual amount	2,653,999	2,330,599
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets), actual amount	3,398,345	3,074,097
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets), actual amount	2,912,529	2,589,374
Tier 1 capital (to average assets):
Tier 1 capital (to average assets), actual amount	$ 2,912,529	$ 2,589,374
Risk Based Ratios [Abstract]
CET1, actual ratio	8.88%	8.58%
Total capital (to risk weighted assets), actual ratio	11.37%	11.31%
Tier 1 capital (to risk-weighted assets), actual ratio	9.75%	9.53%
Tier 1 capital (to average assets), actual ratio	8.42%	9.87%
Bank
Common Equity Tier 1 [Abstract]
CET1, actual amount	$ 2,676,513	$ 2,340,988
CET1 to be well capitalized under prompt corrective action provisions, amount	1,941,522	1,765,915
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets), actual amount	3,262,144	2,925,872
Total capital (to risk weighted assets) to be well capitalized under prompt corrective action provisions, amount	2,986,957	2,716,793
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets), actual amount	2,835,043	2,499,763
Tier 1 capital (to risk weighted assets) to be well capitalized under prompt corrective action provisions, amount	2,389,565	2,173,434
Tier 1 capital (to average assets):
Tier 1 capital (to average assets), actual amount	2,835,043	2,499,763
Tier 1 capital (to average assets) to be well capitalized under prompt corrective action provisions, amount	$ 1,728,988	$ 1,311,620
Risk Based Ratios [Abstract]
CET1, actual ratio	8.96%	8.62%
CET1 to be well capitalized under prompt corrective action provisions, ratio	6.50%	6.50%
Total capital (to risk weighted assets), actual ratio	10.92%	10.77%
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	9.49%	9.20%
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	8.20%	9.53%
Tier 1 capital (to average assets) to be well capitalized under prompt corrective action provisions, ratio	5.00%	5.00%
Basel III, Phase-In Schedule
Common Equity Tier 1 [Abstract]
CET1 for capital adequacy purposes, amount	$ 1,344,825	$ 1,732,501
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets) for capital adequacy purposes, amount	2,390,801	2,683,679
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, amount	1,793,101	2,140,149
Tier 1 capital (to average assets):
Tier 1 capital (to average assets) for capital adequacy purposes, amount	$ 1,383,640	$ 1,049,694
Risk Based Ratios [Abstract]
CET1 for capital adequacy purposes, ratio	4.50%	6.38%
Total capital (to risk weighted assets) for capital adequacy purposes, ratio	8.00%	9.88%
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, ratio	6.00%	7.88%
Tier 1 capital (to average assets) for capital adequacy purposes, ratio	4.00%	4.00%
Basel III, Phase-In Schedule | Bank
Common Equity Tier 1 [Abstract]
CET1 for capital adequacy purposes, amount	$ 1,344,131	$ 1,731,955
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets) for capital adequacy purposes, amount	2,389,565	2,682,833
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, amount	1,792,174	2,139,474
Tier 1 capital (to average assets):
Tier 1 capital (to average assets) for capital adequacy purposes, amount	$ 1,383,190	$ 1,049,296
Risk Based Ratios [Abstract]
CET1 for capital adequacy purposes, ratio	4.50%	6.38%
Total capital (to risk weighted assets) for capital adequacy purposes, ratio	8.00%	9.88%
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, ratio	6.00%	7.88%
Tier 1 capital (to average assets) for capital adequacy purposes, ratio	4.00%	4.00%
Basel III, Phased-In
Common Equity Tier 1 [Abstract]
CET1 for capital adequacy purposes, amount	$ 2,091,591	$ 1,902,354
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets) for capital adequacy purposes, amount	3,137,926	2,853,532
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, amount	2,540,226	2,310,002
Tier 1 capital (to average assets):
Tier 1 capital (to average assets) for capital adequacy purposes, amount	$ 1,383,640	$ 1,049,694
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%
Basel III, Phased-In | Bank
Common Equity Tier 1 [Abstract]
CET1 for capital adequacy purposes, amount	$ 2,090,870	$ 1,901,755
Total capital (to risk-weighted assets):
Total capital (to risk weighted assets) for capital adequacy purposes, amount	3,136,305	2,852,632
Tier 1 capital (to risk-weighted assets):
Tier 1 capital (to risk-weighted assets) for capital adequacy purposes, amount	2,538,913	2,309,274
Tier 1 capital (to average assets):
Tier 1 capital (to average assets) for capital adequacy purposes, amount	$ 1,383,190	$ 1,049,296
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%