Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total		Class A Common Stock	Class B Common Stock	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Additional Paid- in-Capital	Treasury Stock	Retained Earnings (Dividends in Excess of Earnings)	Accumulated Other Comprehensive Income (Loss)	Operating Partnership	Consolidated Joint Ventures
Beginning Balance (in shares) at Dec. 31, 2017					93,641,000	17,668,000
Beginning Balance at Dec. 31, 2017	$ 1,488,146				$ 94	$ 18	$ 1,306,136	$ (31,956)	$ (39,112)	$ (212)	$ 240,861	$ 12,317
Increase Decrease in Stockholders' Equity
Contributions	5,779											5,779
Distributions	(37,591)										(13,191)	(24,400)
Amortization of equity based compensation	6,667						6,667
Grants of restricted stock (in shares)					34,000
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units (in shares)					(56,000)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units	(837)							(837)
Forfeitures (in shares)					(26,000)
Dividends declared	(94,206)								(94,206)
Exchange of noncontrolling interest for common stock (in shares)			4,549,832	(4,549,832)	4,550,000	(4,550,000)
Exchange of noncontrolling interest for common stock	514				$ 5	$ (5)	63,109			(167)	(62,428)
Net income (loss)	194,829								155,911		22,786	16,132
Other comprehensive income (loss)	(9,658)									(8,230)	(1,428)
Rebalancing of ownership percentage between Company and Operating Partnership							(896)			27	869
Ending Balance (in shares) at Sep. 30, 2018					98,143,000	13,118,000
Ending Balance at Sep. 30, 2018	1,553,643				$ 99	$ 13	1,375,016	(32,793)	22,593	(8,582)	187,469	9,828
Beginning Balance (in shares) at Jun. 30, 2018					97,938,000	13,318,000
Beginning Balance at Jun. 30, 2018	1,512,462				$ 99	$ 13	1,370,092	(32,793)	(12,106)	(9,855)	185,158	11,854
Increase Decrease in Stockholders' Equity
Contributions	739											739
Distributions	(14,900)										(4,292)	(10,608)
Amortization of equity based compensation	2,162						2,162
Grants of restricted stock (in shares)					5,000
Dividends declared	(31,931)								(31,931)
Exchange of noncontrolling interest for common stock (in shares)					200,000	(200,000)
Exchange of noncontrolling interest for common stock	202					$ 0	3,000			(24)	(2,774)
Net income (loss)	83,464								66,630		8,991	7,843
Other comprehensive income (loss)	1,445									1,276	169
Rebalancing of ownership percentage between Company and Operating Partnership							(238)			21	217
Ending Balance (in shares) at Sep. 30, 2018					98,143,000	13,118,000
Ending Balance at Sep. 30, 2018	1,553,643				$ 99	$ 13	1,375,016	(32,793)	22,593	(8,582)	187,469	9,828
Beginning Balance (in shares) at Dec. 31, 2018					103,941,000	13,118,000
Beginning Balance at Dec. 31, 2018	1,643,635	[1]			$ 105	$ 13	1,471,157	(32,815)	11,342	(4,649)	188,427	10,055
Increase Decrease in Stockholders' Equity
Contributions	498											498
Distributions	(13,834)										(12,821)	(1,013)
Amortization of equity based compensation	18,336						18,336
Grants of restricted stock (in shares)					1,478,000
Grants of restricted stock					$ 1		(1)
Purchase of treasury stock (in shares)					(40,000)
Purchase of treasury stock	(637)							(637)
Re-issuance of treasury stock (in shares)					92,000
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units (in shares)					(462,000)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units	(8,104)							(8,104)
Forfeitures (in shares)					(9,000)
Dividends declared	(109,375)								(109,375)
Stock dividends (in shares)					1,434,000	181,000
Stock dividends	0				$ 1		23,822		(23,823)
Exchange of noncontrolling interest for common stock (in shares)					1,140,000	(1,140,000)
Exchange of noncontrolling interest for common stock	404				$ 1	$ (1)	16,449			64	(16,109)
Net income (loss)	91,552								81,996		10,247	(691)
Other comprehensive income (loss)	16,775									14,935	1,840
Rebalancing of ownership percentage between Company and Operating Partnership							(164)			17	147
Ending Balance (in shares) at Sep. 30, 2019					107,574,000	12,159,000
Ending Balance at Sep. 30, 2019	1,639,250	[1]			$ 108	$ 12	1,529,599	(41,556)	(39,860)	10,367	171,731	8,849
Beginning Balance (in shares) at Jun. 30, 2019					107,551,000	12,159,000
Beginning Balance at Jun. 30, 2019	1,648,074				$ 108	$ 12	1,526,469	(41,535)	(30,847)	12,171	172,466	9,230
Increase Decrease in Stockholders' Equity
Contributions	306											306
Distributions	(5,034)										(4,283)	(751)
Amortization of equity based compensation	3,575						3,575
Re-issuance of treasury stock (in shares)					24,000
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units (in shares)					(1,000)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units	(21)							(21)
Dividends declared	(36,589)								(36,589)
Net income (loss)	30,948								27,576		3,308	64
Other comprehensive income (loss)	(2,009)									(1,804)	(205)
Rebalancing of ownership percentage between Company and Operating Partnership							(445)				445
Ending Balance (in shares) at Sep. 30, 2019					107,574,000	12,159,000
Ending Balance at Sep. 30, 2019	$ 1,639,250	[1]			$ 108	$ 12	$ 1,529,599	$ (41,556)	$ (39,860)	$ 10,367	$ 171,731	$ 8,849

[1] Includes amounts relating to consolidated variable interest entities. See Note 10.