Operating Leases (Details) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2019 USD ($)		Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)		Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Property Subject to or Available for Operating Lease [Line Items]
Document Period End Date					Sep. 30, 2019
Property operating expense		$ 14,663		$ 6,968	$ 45,227		$ 21,866
Operating Lease, Right-of-Use Asset		$ 219,459			$ 219,459			$ 0
Number of Properties Subject to Ground Leases		58			58
General and Administrative Expense		$ 11,600		11,424	$ 35,540		36,724
Operating Leases, Income Statement, Lease Revenue		(161,262)		(140,905)	(469,315)		(410,848)
Lease, Cost		702			1,603
Straight-Line Rent Receivable		89,361	[1]		89,361	[1]		73,332
Total Operating Leased Assets		244,642			244,642
Operating Lease, Liability		244,358			244,358			0
Operating Leases, Future Minimum Payments Receivable, Current		147,765			147,765
Operating Leases, Future Minimum Payments Receivable, in Two Years		580,865			580,865
Operating Leases, Future Minimum Payments Receivable, in Three Years		570,915			570,915
Operating Leases, Future Minimum Payments Receivable, in Four Years		557,224			557,224
Operating Leases, Future Minimum Payments Receivable, in Five Years		529,256			529,256
Operating Leases, Future Minimum Payments Receivable, Thereafter		4,895,736			4,895,736
Operating Leases, Future Minimum Payments Receivable		7,281,761			7,281,761
Ground Lease Arrangement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Leases, Future Minimum Payments Receivable, Current	[2]	141,626			141,626			520,139	[3]
Operating Leases, Future Minimum Payments Receivable, in Two Years	[2]	556,890			556,890			503,344	[3]
Operating Leases, Future Minimum Payments Receivable, in Three Years	[2]	546,544			546,544			492,165	[3]
Operating Leases, Future Minimum Payments Receivable, in Four Years	[2]	533,426			533,426			477,671	[3]
Operating Leases, Future Minimum Payments Receivable, in Five Years	[2]	506,118			506,118			449,686	[3]
Operating Leases, Future Minimum Payments Receivable, Thereafter	[2]	4,641,759			4,641,759			3,953,717	[3]
Operating Leases, Future Minimum Payments Receivable	[2]	$ 6,926,363			$ 6,926,363			6,396,722	[3]
Ground Lease Arrangement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Lease, Weighted Average Remaining Lease Term		16 years 9 months 18 days			16 years 9 months 18 days
Property operating expense		$ 6,407			$ 18,410
Operating Lease, Right-of-Use Asset		214,106			214,106
Receivable with Imputed Interest, Discount	[4]	137,368			137,368
Operating Lease, Liability	[4]	$ 238,796			$ 238,796
Operating Lease, Weighted Average Discount Rate, Percent		4.95%			4.95%
Operating Leases, Future Minimum Payments Due, Next Twelve Months		$ 6,345	[4]		$ 6,345	[4]		22,867	[5]
Operating Leases, Future Minimum Payments, Due in Two Years		24,592	[4]		24,592	[4]		23,236	[5]
Operating Leases, Future Minimum Payments, Due in Three Years		25,036	[4]		25,036	[4]		23,600	[5]
Operating Leases, Future Minimum Payments, Due in Four Years		24,468	[4]		24,468	[4]		22,996	[5]
Operating Leases, Future Minimum Payments, Due in Five Years		23,812	[4]		23,812	[4]		22,303	[5]
Operating Leases, Future Minimum Payments, Due Thereafter		271,911	[4]		271,911	[4]		257,446	[5]
Operating Leases, Future Minimum Payments Due		376,164	[4]		376,164	[4]		372,448	[5]
Operating Leases, Future Minimum Payments Receivable, Current	[2]	6,139			6,139
Operating Leases, Future Minimum Payments Receivable, in Two Years	[2]	23,975			23,975
Operating Leases, Future Minimum Payments Receivable, in Three Years	[2]	24,371			24,371
Operating Leases, Future Minimum Payments Receivable, in Four Years	[2]	23,798			23,798
Operating Leases, Future Minimum Payments Receivable, in Five Years	[2]	23,138			23,138
Operating Leases, Future Minimum Payments Receivable, Thereafter	[2]	253,977			253,977
Operating Leases, Future Minimum Payments Receivable	[2]	$ 355,398			$ 355,398
Office Lease [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Lease, Weighted Average Remaining Lease Term		7 years			7 years
Operating Lease, Right-of-Use Asset		$ 5,353			$ 5,353
General and Administrative Expense		226			682
Receivable with Imputed Interest, Discount	[6]	984			984
Operating Lease, Liability	[6]	$ 5,562			$ 5,562
Operating Lease, Weighted Average Discount Rate, Percent		4.62%			4.62%
Operating Leases, Future Minimum Payments Due, Next Twelve Months	[6]	$ 214			$ 214			856	[5]
Operating Leases, Future Minimum Payments, Due in Two Years	[6]	856			856			856	[5]
Operating Leases, Future Minimum Payments, Due in Three Years	[6]	884			884			884	[5]
Operating Leases, Future Minimum Payments, Due in Four Years	[6]	967			967			967	[5]
Operating Leases, Future Minimum Payments, Due in Five Years	[6]	967			967			967	[5]
Operating Leases, Future Minimum Payments, Due Thereafter	[6]	2,658			2,658			2,658	[5]
Operating Leases, Future Minimum Payments Due	[6]	6,546			6,546			$ 7,188	[5]
sublease [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Leases, Income Statement, Lease Revenue		$ (5,931)			$ (17,489)
Minimum [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lessee, Operating Lease, Term of Contract		1 year			1 year
Minimum [Member] | Ground Lease Arrangement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lessee, Operating Lease, Term of Contract		2 years			2 years
Maximum [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lessee, Operating Lease, Term of Contract		30 years			30 years
Maximum [Member] | Ground Lease Arrangement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lessee, Operating Lease, Term of Contract		47 years			47 years
Ground Lease Arrangement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Straight-Line Rent Receivable		$ 24,454		$ 0	$ 24,454		$ 0
Ground Lease Arrangement [Member] | sub-lessor [Member]
Property Subject to or Available for Operating Lease [Line Items]
Straight-Line Rent Receivable		$ 25,183			$ 25,183

[1] At September 30, 2019, includes $25.2 million in sub-lessor straight-line rent receivables. Sub-lessor straight-line receivables relate to the Company's operating ground leases. The Company's tenants, who are generally sub-tenants under these ground leases, are responsible for paying the rent under these leases. See Note 16 for information related to the Company's leases.

[2] Included in rental revenue.

[3] Balances as of December 31, 2018 are prior to the adoption of Topic 842.

[4] Included in property operating expense.

[5] Balances as of December 31, 2018 are prior to the adoption of Topic 842.

[6] Included in general and administrative expense.