Leases - Operating Lease Rental Income (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating lease rental income for leased assets
Operating lease rental income recognized	$ 9,700	$ 9,400	$ 8,700
Future minimum rental income under noncancelable operating leases with terms in excess of one year
2017	9,643
2018	9,136
2019	8,620
2020	8,617
2021	8,308
Thereafter	22,589
Total	$ 66,913

Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6454179&loc=d3e41551-112718

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- References

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- Definition

Future rental payments receivable within one year of the balance sheet date under an operating lease.

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- Definition

Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

+ References

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- Definition

Future rental payments receivable within the fourth year from the balance sheet date under an operating lease.

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- Definition

Future rental payments receivable within the third year from the balance sheet date under an operating lease.

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- Definition

Future rental payments receivable within the second year from the balance sheet date under an operating lease.

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- Definition

Future minimum lease payments receivable under operating leases for periods greater than five years following the balance sheet date.

+ References

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- Definition

The total amount of lease revenue recognized for the period for which the lessee was obligated under leasing arrangements regardless of any other events or conditions. This amount excludes contingent revenue and sublease revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=7501430&loc=d3e39896-112707

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