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Summary of Significant Accounting Policies (Prior Period Adjustments) (Details) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2019 | Mar. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items] |  |
Spare parts and equipment sales | $ 17,502 | $ 12,986
Gain (loss) on sale of leased equipment | 9,570 | 545
Cost of spare parts and equipment sales | 14,412 | 11,388
Cash flows provided by operating activities | 35,628 | 35,281
Cash flows provided by financing activities | (42,250) | 91,683
Impacts from ASC 606 |  |
Revenue, Initial Application Period Cumulative Effect Transition [Line Items] |  |
Spare parts and equipment sales |  | 6,700
Gain (loss) on sale of leased equipment |  | (100)
Cost of spare parts and equipment sales |  | 6,600
Cash flows provided by operating activities |  | $ 4,900
Cash flows provided by financing activities | $ (4,500) |

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- Definition The net gain (loss) arising from the lessor's sale of assets held- or available-for-lease under contractual arrangements classified as operating leases. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 40 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=77911379&loc=d3e44908-112734 + Details
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- Definition Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3521-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
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