Commitments and Contingencies - Future minimum capital lease payments (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Future minimum payments on capital leases:
2018	$ 11,269
2019	11,551
2020	11,840
2021	12,136
2022	12,439
2023 - 2028	74,142
Total minimum future lease payments	$ 133,377

Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77914019&loc=d3e50824-112756

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Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of minimum lease payments for sale-leaseback transactions accounted for using the deposit method or as a financing due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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