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The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively.

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Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable.

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Present value of lessee's discounted obligation for lease payments from operating lease.

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Amount of lessee's right to use underlying asset under operating lease.

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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Balance sheet impact
Operating lease right-of-use assets	$ 194,732		$ 194,732		$ 92,984
Operating lease liabilities	204,424		204,424		102,912
Income statement impact
Rental revenue	121,479	$ 106,867	353,563	$ 309,837
ASU 2016-02
Balance sheet impact
Operating lease right-of-use assets					92,984
Operating lease liabilities					102,912
As Previously Reported \| ASU 2016-02
Balance sheet impact
Deferred rent payable					9,928
As Previously Reported \| ASU 2018-11
Income statement impact
Rental revenue	74,321	66,657	219,497	195,761
Adjustment \| ASU 2016-02
Balance sheet impact
Operating lease right-of-use assets					92,984
Operating lease liabilities					102,912
Deferred rent payable					$ (9,928)
Adjustment \| ASU 2018-11
Income statement impact
Rental revenue	(74,321)	(66,657)	(219,497)	(195,761)
Power Revenue \| As Previously Reported \| ASU 2018-11
Income statement impact
Revenue	40,967	35,110	116,356	98,381
Power Revenue \| Adjustment \| ASU 2018-11
Income statement impact
Revenue	(40,967)	(35,110)	(116,356)	(98,381)
Tenant Reimbursement And Other Revenue \| As Previously Reported \| ASU 2018-11
Income statement impact
Revenue	3,302	2,185	8,892	6,790
Tenant Reimbursement And Other Revenue \| Adjustment \| ASU 2018-11
Income statement impact
Revenue	(3,302)	(2,185)	(8,892)	(6,790)
Rental Power And Related Revenue
Income statement impact
Rental revenue	118,590	103,952	344,745	300,932
Rental Power And Related Revenue \| ASU 2018-11
Income statement impact
Revenue	118,590	103,952	344,745	300,932
Rental Power And Related Revenue \| Adjustment \| ASU 2018-11
Income statement impact
Revenue	$ 118,590	$ 103,952	$ 344,745	$ 300,932