Operating Leases (Details) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2019 USD ($)		Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)		Jun. 30, 2018 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)		Mar. 31, 2018 USD ($)
Property Subject to or Available for Operating Lease [Line Items]
Document Period End Date					Jun. 30, 2019
Property operating expense		$ 14,771		$ 7,334	$ 30,564		$ 14,898
Operating Lease, Right-of-Use Asset		$ 220,758			$ 220,758				$ 0
Number of Properties Subject to Ground Leases		58			58
General and Administrative Expense		$ 12,230		12,976	$ 24,360		25,300
Operating Leases, Income Statement, Lease Revenue		(157,330)		$ (137,019)	(308,053)		$ (269,943)
Lease, Cost		456			901
Straight-Line Rent Receivable		95,449	[1]		95,449	[1]			73,332
Total Operating Leased Assets		245,601			245,601
Operating Lease, Liability		245,372			245,372				0
Operating Leases, Future Minimum Payments Receivable, Current		291,182			291,182
Operating Leases, Future Minimum Payments Receivable, in Two Years		571,789			571,789
Operating Leases, Future Minimum Payments Receivable, in Three Years		561,194			561,194
Operating Leases, Future Minimum Payments Receivable, in Four Years		545,989			545,989
Operating Leases, Future Minimum Payments Receivable, in Five Years		517,044			517,044
Operating Leases, Future Minimum Payments Receivable, Thereafter		4,736,991			4,736,991
Operating Leases, Future Minimum Payments Receivable		7,224,189			7,224,189
Ground Lease Arrangement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Leases, Future Minimum Payments Receivable, Current	[2]	279,551			279,551				520,139	[3]
Operating Leases, Future Minimum Payments Receivable, in Two Years	[2]	548,065			548,065				503,344	[3]
Operating Leases, Future Minimum Payments Receivable, in Three Years	[2]	537,074			537,074				492,165	[3]
Operating Leases, Future Minimum Payments Receivable, in Four Years	[2]	522,442			522,442				477,671	[3]
Operating Leases, Future Minimum Payments Receivable, in Five Years	[2]	494,157			494,157				449,686	[3]
Operating Leases, Future Minimum Payments Receivable, Thereafter	[2]	4,484,878			4,484,878				3,953,717	[3]
Operating Leases, Future Minimum Payments Receivable	[2]	$ 6,866,167			$ 6,866,167				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		17 years			17 years
Property operating expense		$ 6,065			$ 12,003
Operating Lease, Right-of-Use Asset		215,244			215,244
Receivable with Imputed Interest, Discount	[4]	139,261			139,261
Operating Lease, Liability	[4]	$ 239,662			$ 239,662
Operating Lease, Weighted Average Discount Rate, Percent		4.95%			4.95%
Operating Leases, Future Minimum Payments Due, Next Twelve Months		$ 11,973	[4]		$ 11,973	[4]			22,867	[5]
Operating Leases, Future Minimum Payments, Due in Two Years		24,341	[4]		24,341	[4]			23,236	[5]
Operating Leases, Future Minimum Payments, Due in Three Years		24,785	[4]		24,785	[4]			23,600	[5]
Operating Leases, Future Minimum Payments, Due in Four Years		24,217	[4]		24,217	[4]			22,996	[5]
Operating Leases, Future Minimum Payments, Due in Five Years		23,560	[4]		23,560	[4]			22,303	[5]
Operating Leases, Future Minimum Payments, Due Thereafter		270,047	[4]		270,047	[4]			257,446	[5]
Operating Leases, Future Minimum Payments Due		378,923	[4]		378,923	[4]			372,448	[5]
Operating Leases, Future Minimum Payments Receivable, Current	[2]	11,631			11,631
Operating Leases, Future Minimum Payments Receivable, in Two Years	[2]	23,724			23,724
Operating Leases, Future Minimum Payments Receivable, in Three Years	[2]	24,120			24,120
Operating Leases, Future Minimum Payments Receivable, in Four Years	[2]	23,547			23,547
Operating Leases, Future Minimum Payments Receivable, in Five Years	[2]	22,887			22,887
Operating Leases, Future Minimum Payments Receivable, Thereafter	[2]	252,113			252,113
Operating Leases, Future Minimum Payments Receivable	[2]	$ 358,022			$ 358,022
Office Lease [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Lease, Weighted Average Remaining Lease Term		7 years 3 months 18 days			7 years 3 months 18 days
Operating Lease, Right-of-Use Asset		$ 5,514			$ 5,514
General and Administrative Expense		226			456
Receivable with Imputed Interest, Discount	[6]	1,050			1,050
Operating Lease, Liability	[6]	$ 5,710			$ 5,710
Operating Lease, Weighted Average Discount Rate, Percent		4.62%			4.62%
Operating Leases, Future Minimum Payments Due, Next Twelve Months	[6]	$ 428			$ 428				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]	6,760			6,760				$ 7,188	[5]
sublease [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating Leases, Income Statement, Lease Revenue		$ (5,835)			$ (11,558)
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		31 years			31 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		$ 24,843			$ 24,843			$ 24,454			$ 0

[1] At June 30, 2019, includes $24.8 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.