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Subsequent Events (Narrative) (Details) - USD ($) | Oct. 30, 2020 | Oct. 09, 2020 | Nov. 05, 2020 | Nov. 02, 2020 | Sep. 30, 2020 | Dec. 31, 2019 | Dec. 31, 2013
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Subsequent Event [Line Items] |  |  |  |  |  |  |
Financing agreements ($4,080,461 and $0 held at fair value, respectively) |  |  |  |  | $ 4,851,121,000 | $ 10,031,606,000 |
Stock repurchase program, authorized amount |  |  |  |  |  |  | $ 10,000,000
Number of remaining shares authorized to be repurchased under the Repurchase Program (in shares) |  |  |  |  | 6,616,355 |  |
Common stock, shares outstanding (in shares) |  |  |  |  | 453,333,000 | 452,369,000 |
Subsequent Event |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Repayments of debt | $ 81,250,000 | $ 400,000,000 |  |  |  |  |
Stock repurchase program, authorized amount |  |  |  | $ 250,000,000 |  |  |
Subsequent Event | Non-QM Loans [Member] |  |  |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |  |  |
Financing agreements ($4,080,461 and $0 held at fair value, respectively) |  |  | $ 570,000,000 |  |  |  |
Cash |  |  | $ 125,100,000 |  |  |  |

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- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=118262064&loc=SL116631418-115840 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section 45 -Paragraph 21 -URI http://asc.fasb.org/extlink&oid=118262064&loc=SL116631419-115840 + Details
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