Derivative Instruments and Hedging Activities U.S. Treasury Futures (Details) - USD ($) |
Mar. 31, 2019 |
Dec. 31, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|---|
| Derivative [Line Items] | ||||
| Notional | $ 58,777,783,000 | $ 36,528,169,000 | $ 18,429,288,000 | $ 31,226,878,000 |
| Derivative Financial Instruments, Assets [Member] | ||||
| Derivative [Line Items] | ||||
| Notional | 58,730,710,000 | 36,258,904,000 | ||
| Fair Value | 336,112,000 | $ 319,981,000 | ||
| U.S. Treasury Futures [Member] | Derivative Financial Instruments, Assets [Member] | ||||
| Derivative [Line Items] | ||||
| Notional | 1,310,000,000 | |||
| Fair Value | $ 3,727,000 |
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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