Segments - Schedule of Each Reportable Segment Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended				12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2015
Revenues
Rental income	$ 57,465					$ 586,530
Tenant reimbursement income	5,865					50,885
Fee and other income	2,805					24,993
Total revenues	66,135	$ 170,528	$ 167,726	$ 162,928	$ 161,226	662,408
Total expenses	62,699					591,789
Operating income (loss)	3,436					70,619
Income from real estate fund investments	1,412					37,975
Income from unconsolidated joint ventures	938					6,850
Unrealized gain on interest rate swaps	15,084					75,760
Interest and other income (loss), net	(179)					871
Interest and debt expense	(43,743)					(168,366)
Formation related costs	(143,437)
Gain on consolidation of an unconsolidated joint venture	239,716
Net income before income taxes	73,227					23,709
Income tax (expense) benefit	(505)					(2,566)
Net income	72,722					21,143
Depreciation and amortization	34,481					294,624
General and administrative	2,207					42,056
Interest and debt expense	43,743					168,366
Transfer taxes due in connection with the sale of shares by a former joint venture partner						10,355
Income tax expense (benefit)	505					2,566
Net Operating Income from unconsolidated joint ventures	1,680					16,580
Income from real estate fund investments	(1,412)					(37,975)
Income from unconsolidated joint ventures	(938)					(6,850)
Fee income	(1,176)					(10,248)
Unrealized gain on interest rate swaps	(15,084)					(75,760)
Interest and other (income) loss, net	179					(871)
Gain on consolidation of unconsolidated joint ventures	(239,716)
Net Operating Income	42,040					423,986
Total assets	9,030,441	8,794,143				8,794,143
Total liabilities	3,475,488	3,483,593				3,483,593
Total equity	5,554,953	5,310,550				5,310,550
Total formation related costs	143,437
Transfer Taxes [Member]
Revenues
Transfer taxes due in connection with the sale of shares by a former joint venture partner						5,872
Deal Cost [Member]
Revenues
Transfer taxes due in connection with the sale of shares by a former joint venture partner						4,483
Owned Properties [Member]
Revenues
Rental income	57,169					583,825
Tenant reimbursement income	5,865					50,885
Fee and other income	1,629					14,737
Total revenues	64,663					649,447
Total expenses	61,091					541,774
Operating income (loss)	3,572					107,673
Income from unconsolidated joint ventures	938					6,734
Unrealized gain on interest rate swaps	15,084					75,760
Interest and other income (loss), net	30					367
Interest and debt expense	(41,633)					(160,058)
Net income before income taxes	(22,009)					30,476
Income tax (expense) benefit	(475)					310
Net income	(22,484)					30,786
Depreciation and amortization	34,378					293,433
General and administrative	91
Interest and debt expense	41,633					160,058
Income tax expense (benefit)	475					(310)
Net Operating Income from unconsolidated joint ventures	1,680					16,210
Income from unconsolidated joint ventures	(938)					(6,734)
Unrealized gain on interest rate swaps	(15,084)					(75,760)
Interest and other (income) loss, net	(30)					(367)
Net Operating Income	39,721					417,316
Total assets	8,345,966	8,172,529				8,172,529
Total liabilities	3,350,798	3,309,104				3,309,104
Total equity	4,995,168	4,863,425				4,863,425
Other [Member]
Revenues
Rental income	296					2,705
Fee and other income	1,176					10,256
Total revenues	1,472					12,961
Total expenses	1,608					50,015
Operating income (loss)	(136)					(37,054)
Income from real estate fund investments	1,412					37,975
Income from unconsolidated joint ventures						116
Interest and other income (loss), net	(209)					504
Interest and debt expense	(2,110)					(8,308)
Formation related costs	(143,437)
Gain on consolidation of an unconsolidated joint venture	239,716
Net income before income taxes	95,236					(6,767)
Income tax (expense) benefit	(30)					(2,876)
Net income	95,206					(9,643)
Depreciation and amortization	103					1,191
General and administrative	2,116					42,056
Interest and debt expense	2,110					8,308
Income tax expense (benefit)	30					2,876
Net Operating Income from unconsolidated joint ventures						370
Income from real estate fund investments	(1,412)					(37,975)
Income from unconsolidated joint ventures						(116)
Fee income	(1,176)					(10,248)
Interest and other (income) loss, net	209					(504)
Gain on consolidation of unconsolidated joint ventures	(239,716)
Net Operating Income	2,319					6,670
Total assets	684,475	621,614				621,614
Total liabilities	124,690	174,489				174,489
Total equity	559,785	$ 447,125				447,125
Total formation related costs	$ 143,437
Other [Member] | Transfer Taxes [Member]
Revenues
Transfer taxes due in connection with the sale of shares by a former joint venture partner						5,872
Other [Member] | Deal Cost [Member]
Revenues
Transfer taxes due in connection with the sale of shares by a former joint venture partner						$ 4,483