Fair Value Measurements - Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets at fair value and gains (losses) recorded
Equipment held for sale	$ 629		$ 789
Total losses on equipment held for lease	1,105	$ 0
Total losses on equipment held for sale	0	0
Total losses on assets	1,105	$ 0
Assets Written Down to Fair Value
Assets at fair value and gains (losses) recorded
Equipment held for lease	0		17,756
Equipment held for sale	0		472
Assets at fair value	0		18,228
Assets Written Down to Fair Value \| Level 1
Assets at fair value and gains (losses) recorded
Equipment held for lease	0
Equipment held for sale	0
Assets at fair value	0
Assets Written Down to Fair Value \| Level 2
Assets at fair value and gains (losses) recorded
Equipment held for lease	0		17,756
Equipment held for sale	0		472
Assets at fair value	0		$ 18,228
Assets Written Down to Fair Value \| Level 3
Assets at fair value and gains (losses) recorded
Equipment held for lease	0
Equipment held for sale	0
Assets at fair value	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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Equipment held for sale.

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Amount of gain (loss) in equipment held for sale recorded during the period.

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