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Derivative Financial Instruments - Narrative (Details) - USD ($) | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2015 | Sep. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2014
1:3 basis swaps |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Weighted average basis point paid |  |  | 0.097% |  | 0.094% |
Interest rate swap | Interest rate swaps - floor income hedges |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Amounts received to terminate derivative instruments |  |  |  | $ 2,100,000 |  |
Amounts paid to terminate derivative instruments |  |  | $ 16,500,000 |  |  |
Notional amount, terminated |  |  | $ 700,000,000.0 | $ 100,000,000.0 |  |
Interest rate swap options - floor income hedges |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Payments to enter into derivative instruments |  |  |  |  | $ 4,600,000 | $ 9,100,000
Fixed interest rate of swap option |  |  | 3.21% |  |  |
Interest rate caps |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Payments to enter into derivative instruments | $ 300,000 | $ 2,900,000 |  |  |  |

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- Definition The percentage points added to the reference rate to compute the variable rate on the interest rate derivative. + References No definition available. + Details
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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. + References No definition available. + Details
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- Definition Fixed interest rate that will be received or paid upon exercise of the interest rate swaption contract. + References No definition available. + Details
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- Definition The increase (decrease) during the reporting period in the aggregate value of financial instruments used in operating activities, including trading securities, risk management instruments, and other short-term trading instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 + Details
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- Definition The cash outflow for a financial contract that meets the hedge criteria as either cash flow hedge, fair value hedge or hedge of net investment in foreign operations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 27 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3581-108585 + Details
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- Definition The cash inflow from a financial contract that meets the hedge criteria as either cash flow hedge, fair value hedge or hedge of net investment in foreign operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 27 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3581-108585 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585 + Details
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