CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Class A Common Stock	Total Stockholders’ Equity	Common Stock Class A Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Gain (Loss)	Cumulative Dividends in Excess of Earnings	Noncontrolling Interests
Beginning balance at Dec. 31, 2016	$ 1,780,417		$ 1,687,274	$ 1,417	$ 2,754,818	$ 0	$ (1,068,961)	$ 93,143
Beginning balance (in shares) at Dec. 31, 2016				141,719,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in HTA	1,624,222		1,624,222	$ 586	1,623,636
Issuance of common stock in HTA (in shares)				58,623,000
Issuance of operating partnership units in HTALP in connection with an acquisition	610							610
Share-based award transactions, net	3,839		3,839	$ 2	3,837
Share-based award transactions, net (in shares)				198,000
Repurchase and cancellation of common stock	(3,339)		(3,339)	$ (1)	(3,338)
Repurchase and cancellation of common stock (in shares)				(114,000)
Redemption of noncontrolling interest and other	0		5,532	$ 2	5,530			(5,532)
Redemption of noncontrolling interest and other (in shares)				221,000
Dividends declared	(105,924)		(103,273)				(103,273)	(2,651)
Net income	8,096		7,627				7,627	469
Other comprehensive gain (loss)	(836)		(816)			(816)		(20)
Ending balance at Jun. 30, 2017	3,307,085		3,221,066	$ 2,006	4,384,483	(816)	(1,164,607)	86,019
Ending balance (in shares) at Jun. 30, 2017				200,647,000
Beginning balance at Dec. 31, 2017	3,363,448		3,278,782	$ 2,049	4,508,528	274	(1,232,069)	84,666
Beginning balance (in shares) at Dec. 31, 2017		204,892,118		204,892,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in HTA	72,814		72,814	$ 25	72,789
Issuance of common stock in HTA (in shares)				2,550,000
Share-based award transactions, net	5,703		5,703	$ 3	5,700
Share-based award transactions, net (in shares)				296,000
Repurchase and cancellation of common stock	(11,553)		(11,553)	$ (4)	(11,549)
Repurchase and cancellation of common stock (in shares)				(429,000)
Redemption of noncontrolling interest and other	0		4,907	$ 2	4,905			(4,907)
Redemption of noncontrolling interest and other (in shares)				184,000
Dividends declared	(128,398)		(125,838)				(125,838)	(2,560)
Net income	25,626		25,148				25,148	478
Other comprehensive gain (loss)	1,114		1,093			1,093		21
Ending balance at Jun. 30, 2018	$ 3,328,754		$ 3,251,056	$ 2,075	$ 4,580,373	$ 1,367	$ (1,332,759)	$ 77,698
Ending balance (in shares) at Jun. 30, 2018		207,493,355		207,493,000