Shareholders' Equity / Partners' Capital - Participating Preferred Shares (Details) $ / shares in Units, $ in Thousands			3 Months Ended					12 Months Ended
	Apr. 05, 2018 market $ / shares shares	Oct. 03, 2017 market $ / shares shares	Sep. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2018 USD ($)	Sep. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) market $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)
Class of Stock [Line Items]
Preferred shares, shares outstanding (in shares) | shares								35,350,000	35,350,000
Current Liquidation Value								$ 883,750	$ 883,750
Number of top markets used for purchase price index | market								20
Dividend rate, percentage cap								9.00%
Convertible preferred stock converted to other securities								$ 0	$ 32,215	$ 42,416
Series D Perpetual Preferred Shares/Units
Class of Stock [Line Items]
Dividend Rate								6.50%
Preferred shares, shares outstanding (in shares) | shares								10,750,000	10,750,000
Current Liquidation Value								$ 268,750	$ 268,750
Series E Perpetual Preferred Stock
Class of Stock [Line Items]
Dividend Rate								6.35%
Preferred shares, shares outstanding (in shares) | shares								9,200,000	9,200,000
Current Liquidation Value								$ 230,000	$ 230,000
Series F Perpetual Preferred Stock
Class of Stock [Line Items]
Dividend Rate						5.875%		5.875%
Preferred shares, shares outstanding (in shares) | shares								6,200,000	6,200,000
Current Liquidation Value								$ 155,000	$ 155,000
Liquidation preference per share (in dollars per share) | $ / shares						$ 25.00
Gross proceeds under issuance of preferred shares						$ 155,000
Issuance of perpetual preferred shares, net of offering costs (in shares) | shares						6,200,000
Offering costs						$ 5,300
Series G Perpetual Preferred Stock
Class of Stock [Line Items]
Dividend Rate					5.875%			5.875%
Preferred shares, shares outstanding (in shares) | shares								4,600,000	4,600,000
Current Liquidation Value								$ 115,000	$ 115,000
Liquidation preference per share (in dollars per share) | $ / shares					$ 25.00
Gross proceeds under issuance of preferred shares					$ 115,000
Issuance of perpetual preferred shares, net of offering costs (in shares) | shares					4,600,000
Offering costs					$ 4,100
Series H Perpetual Preferred Stock
Class of Stock [Line Items]
Dividend Rate			6.25%					6.25%
Preferred shares, shares outstanding (in shares) | shares								4,600,000	4,600,000
Current Liquidation Value								$ 115,000	$ 115,000
Liquidation preference per share (in dollars per share) | $ / shares			$ 25.00					$ 25.00
Gross proceeds under issuance of preferred shares			$ 115,000
Issuance of perpetual preferred shares, net of offering costs (in shares) | shares			4,600,000
Offering costs			$ 4,400
Class A common shares/units
Class of Stock [Line Items]
Issuance of perpetual preferred shares, net of offering costs (in shares) | shares					13,800,000		14,842,982
Offering costs					$ 9,200		$ 400	$ 0	$ 0	10,637
Percent of cumulative change in value of an index	50.00%	50.00%						50.00%
Stated value per share | $ / shares	$ 0.01	$ 0.01			$ 0.01		$ 0.01	$ 0.01	$ 0.01
Repurchase of class A units (in shares) | shares	10,848,827	12,398,276
Stock exchange ratio	1.4275	1.3106
Number of markets used in calculation | market	20	20
Maximum internal rate of return	9.00%
Convertible preferred stock converted to other securities				$ 32,200
Preferred stock redemption premium										$ 42,400
Series C Preferred Stock
Class of Stock [Line Items]
Dividend Rate	5.50%							5.50%	5.50%
Liquidation preference per share (in dollars per share) | $ / shares								$ 25.00
Stock issued during period, shares, conversion of convertible securities | shares	7,600,000
Series A Participating Preferred Stock
Class of Stock [Line Items]
Dividend Rate		5.00%						5.00%		5.00%
Liquidation preference per share (in dollars per share) | $ / shares								$ 25.00
Stock issued during period, shares, conversion of convertible securities | shares		5,060,000
Series B Participating Preferred Stock
Class of Stock [Line Items]
Dividend Rate		5.00%						5.00%		5.00%
Liquidation preference per share (in dollars per share) | $ / shares								$ 25.00
Stock issued during period, shares, conversion of convertible securities | shares		4,400,000