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)	Noncontrolling Interests Operating Partnership	Noncontrolling Interests in Consolidated Joint Ventures
Beginning Balance (in shares) at Dec. 31, 2014					51,432,000	47,647,000
Beginning Balance at Dec. 31, 2014	$ 1,505,207				$ 51	$ 0	$ 725,538	$ 0	$ 44,187	$ 15,656	$ 711,674	$ 8,101
Increase Decrease in Stockholders' Equity
Contributions	74											74
Distributions	(72,603)										(68,673)	(3,930)
Amendment of the par value of the Class B shares from no par value per share to $0.001 per share	0					$ 47					(47)
Equity based compensation	13,788						417				13,371
Grants of restricted stock (in shares)					700,000
Grants of restricted stock	0				$ 1		(1)
Purchase of treasury stock (in shares)					(84,000)
Purchase of treasury stock	(994)							(994)
Re-issuance of treasury stock (in shares)					26,000
Re-issuance of treasury stock	0
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units (in shares)					(262,000)	(5,000)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units	(4,897)							(4,818)			(79)
Forfeitures (in shares)					(188,000)
Forfeitures	0
Dividends declared	(57,390)								(57,390)
Exchange of noncontrolling interest for common stock (in shares)			3,586,546	(3,586,546)	3,586,000	(3,586,000)
Exchange of noncontrolling interest for common stock	0				$ 3	$ (3)	53,011			645	(53,656)
Adjustment for deferred taxes/tax receivable agreement as a result of the exchange of Class B shares	(1,366)						(1,366)
Net income (loss)	146,134								73,821		70,745	1,568
Other comprehensive income (loss)	(36,545)									(20,046)	(16,499)
Rebalancing of ownership percentage between Company and Operating Partnership	0						(733)			189	544
Ending Balance (in shares) at Dec. 31, 2015					55,210,000	44,056,000
Ending Balance at Dec. 31, 2015	1,491,408				$ 55	$ 44	776,866	(5,812)	60,618	(3,556)	657,380	5,813
Increase Decrease in Stockholders' Equity
Contributions	250										250
Distributions	(40,562)										(39,805)	(757)
Equity based compensation	17,640						516				17,124
Grants of restricted stock (in shares)					794,000
Grants of restricted stock	0				$ 1		(1)
Purchase of treasury stock (in shares)					(424,000)
Purchase of treasury stock	(4,652)							(4,652)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units (in shares)					(73,000)	(1,000)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units	(786)							(780)			(6)
Forfeitures (in shares)					(48,000)
Forfeitures	0
Dividends declared	(74,393)								(74,393)
Stock dividends (in shares)					5,606,000	4,469,000
Stock dividends	0				$ 6	$ 4	64,090		(64,100)
Exchange of noncontrolling interest for common stock (in shares)			10,521,149	(10,521,149)	10,521,000	(10,521,000)
Exchange of noncontrolling interest for common stock	0				$ 10	$ (10)	144,629			1,202	(145,831)
Adjustment for deferred taxes/tax receivable agreement as a result of the exchange of Class B shares	(1,590)						(1,590)
Net income (loss)	113,720								66,727		47,131	(138)
Other comprehensive income (loss)	8,519									3,420	5,099
Rebalancing of ownership percentage between Company and Operating Partnership	0						7,797			299	(8,096)
Ending Balance (in shares) at Dec. 31, 2016					71,586,000	38,003,000
Ending Balance at Dec. 31, 2016	1,509,554				$ 72	$ 38	992,307	(11,244)	(11,148)	1,365	533,246	4,918
Increase Decrease in Stockholders' Equity
Contributions	7,479										0	7,479
Distributions	(42,524)										(42,218)	(306)
Equity based compensation	18,965						18,965				0
Grants of restricted stock (in shares)					1,997,000
Grants of restricted stock	0				$ 1		(1)
Purchase of treasury stock (in shares)					(190,000)
Purchase of treasury stock	(2,588)							(2,588)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units (in shares)					(1,323,000)
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock and units	(18,125)				$ (1)			(18,124)
Forfeitures (in shares)					(10,000)
Forfeitures	0
Dividends declared	(105,921)								(105,921)
Stock dividends (in shares)					814,000	432,000
Stock dividends	0				$ 1	$ 1	17,317		(17,319)
Exchange of noncontrolling interest for common stock (in shares)			20,767,407	(20,767,407)	20,767,000	(20,767,000)
Exchange of noncontrolling interest for common stock	(2,353)				$ 21	$ (21)	280,714			1,696	(284,763)
Net income (loss)	125,879								95,276		30,377	226
Other comprehensive income (loss)	(2,220)									(2,915)	695
Rebalancing of ownership percentage between Company and Operating Partnership	0						(3,166)			(358)	3,524
Ending Balance (in shares) at Dec. 31, 2017					93,641,000	17,668,000
Ending Balance at Dec. 31, 2017	$ 1,488,146	[1]			$ 94	$ 18	$ 1,306,136	$ (31,956)	$ (39,112)	$ (212)	$ 240,861	$ 12,317

[1] Includes amounts relating to consolidated variable interest entities. See Note 3.