Schedule of Underlying Assets of Repurchase Agreements when Amount of Repurchase Agreements Exceeds 10 Percent of Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	$ 31,196,419	$ 25,530,229
Available-for-sale Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	29,575,948	24,240,507
Mortgage Servicing Rights [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	530,222	685,683
Restricted Cash and Cash Equivalents [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	919,010	416,696
Due From Counterparties [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	102,365	110,695
Derivative Financial Instruments, Assets [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	68,874	70,191
US Treasury Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets pledged or restricted as collateral for repurchase agreements	$ 0	$ 6,457