Segment Reporting - Components of Segment Profit for Each Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenues:
Rental revenue	$ 137,999	$ 141,071	$ 286,112	$ 284,488
Intercompany rental revenue	0	0	0	0
Observatory revenue	86	32,895	19,630	53,464
Lease termination fees	1,033	363	1,244	751
Third-party management and other fees	301	331	647	651
Other revenue and fees	1,611	1,584	3,621	4,183
Total revenues	141,030	176,244	311,254	343,537
Operating expenses:
Property operating expenses	29,750	40,227	71,218	83,182
Intercompany rent expense	0	0	0	0
Ground rent expense	2,332	2,332	4,663	4,663
General and administrative expenses	18,149	15,998	34,100	30,024
Observatory expenses	4,002	8,360	12,156	15,935
Real estate taxes	29,579	28,267	58,833	56,499
Impairment charge	4,101	0	4,101	0
Depreciation and amortization	52,783	44,821	98,876	90,919
Total operating expenses	140,696	140,005	283,947	281,222
Total operating income	334	36,239	27,307	62,315
Other income (expense):
Interest income	1,526	3,899	2,163	7,638
Interest expense	(23,928)	(20,597)	(43,546)	(41,286)
Loss on early extinguishment of debt	0	0	(86)	0
Income (loss) before income taxes	(22,068)	19,541	(14,162)	28,667
Income tax (expense) benefit	2,450	(611)	2,832	119
Net income (loss)	(19,618)	18,930	(11,330)	28,786
Segment assets	4,550,395	4,155,575	4,550,395	4,155,575	$ 3,931,834
Expenditures for segment assets	21,095	61,972	48,904	120,292
Intersegment Elimination
Revenues:
Rental revenue	0	0	0	0
Intercompany rental revenue	(4,053)	(21,491)	(15,589)	(35,512)
Observatory revenue	0	0	0	0
Lease termination fees	0	0	0	0
Third-party management and other fees	0	0	0	0
Other revenue and fees	0	0	0	0
Total revenues	(4,053)	(21,491)	(15,589)	(35,512)
Operating expenses:
Property operating expenses	0	0	0	0
Intercompany rent expense	(4,053)	(21,491)	(15,589)	(35,512)
Ground rent expense	0	0	0	0
General and administrative expenses	0	0	0	0
Observatory expenses	0	0	0	0
Real estate taxes	0	0	0	0
Impairment charge	0		0
Depreciation and amortization	0	0	0	0
Total operating expenses	(4,053)	(21,491)	(15,589)	(35,512)
Total operating income	0	0	0	0
Other income (expense):
Interest income	0	0	0	0
Interest expense	0	0	0	0
Loss on early extinguishment of debt	0		0
Income (loss) before income taxes	0	0	0	0
Income tax (expense) benefit	0	0	0	0
Net income (loss)	0	0	0	0
Segment assets	0	0	0	0
Expenditures for segment assets	0	0	0	0
Real Estate
Operating expenses:
Impairment charge	4,100
Real Estate | Operating Segments
Revenues:
Rental revenue	137,999	141,071	286,112	284,488
Intercompany rental revenue	4,053	21,491	15,589	35,512
Observatory revenue	0	0	0	0
Lease termination fees	1,033	363	1,244	751
Third-party management and other fees	301	331	647	651
Other revenue and fees	1,611	1,584	3,621	4,183
Total revenues	144,997	164,840	307,213	325,585
Operating expenses:
Property operating expenses	29,750	40,227	71,218	83,182
Intercompany rent expense	0	0	0	0
Ground rent expense	2,332	2,332	4,663	4,663
General and administrative expenses	18,149	15,998	34,100	30,024
Observatory expenses	0	0	0	0
Real estate taxes	29,579	28,267	58,833	56,499
Impairment charge	4,101		4,101
Depreciation and amortization	52,758	44,813	98,843	90,904
Total operating expenses	136,669	131,637	271,758	265,272
Total operating income	8,328	33,203	35,455	60,313
Other income (expense):
Interest income	1,441	3,899	2,078	7,638
Interest expense	(23,928)	(20,597)	(43,546)	(41,286)
Loss on early extinguishment of debt	0		(86)
Income (loss) before income taxes	(14,159)	16,505	(6,099)	26,665
Income tax (expense) benefit	(269)	(261)	(496)	(495)
Net income (loss)	(14,428)	16,244	(6,595)	26,170
Segment assets	4,305,105	3,891,038	4,305,105	3,891,038
Expenditures for segment assets	20,100	47,433	46,672	91,964
Observatory | Operating Segments
Revenues:
Rental revenue	0	0	0	0
Intercompany rental revenue	0	0	0	0
Observatory revenue	86	32,895	19,630	53,464
Lease termination fees	0	0	0	0
Third-party management and other fees	0	0	0	0
Other revenue and fees	0	0	0	0
Total revenues	86	32,895	19,630	53,464
Operating expenses:
Property operating expenses	0	0	0	0
Intercompany rent expense	4,053	21,491	15,589	35,512
Ground rent expense	0	0	0	0
General and administrative expenses	0	0	0	0
Observatory expenses	4,002	8,360	12,156	15,935
Real estate taxes	0	0	0	0
Impairment charge	0		0
Depreciation and amortization	25	8	33	15
Total operating expenses	8,080	29,859	27,778	51,462
Total operating income	(7,994)	3,036	(8,148)	2,002
Other income (expense):
Interest income	85	0	85	0
Interest expense	0	0	0	0
Loss on early extinguishment of debt	0		0
Income (loss) before income taxes	(7,909)	3,036	(8,063)	2,002
Income tax (expense) benefit	2,719	(350)	3,328	614
Net income (loss)	(5,190)	2,686	(4,735)	2,616
Segment assets	245,290	264,537	245,290	264,537
Expenditures for segment assets	$ 995	$ 14,539	$ 2,232	$ 28,328