Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	$ 18,446,751	$ 31,196,419
Available-for-sale Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	17,661,378	29,575,948
Mortgage Servicing Rights [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	368,779	530,222
Restricted Cash and Cash Equivalents [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	299,579	919,010
Due From Counterparties [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	43,794	102,365
Derivative Financial Instruments, Assets [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	$ 73,221	$ 68,874