Shareholders' Equity - Narrative (Details)									1 Months Ended				12 Months Ended
	Oct. 23, 2019 USD ($) $ / shares	Sep. 24, 2019 $ / shares	Mar. 13, 2019 USD ($)	Oct. 23, 2018 USD ($) $ / shares	Oct. 09, 2018 $ / shares	Mar. 14, 2018 USD ($)	Mar. 15, 2017 USD ($)	Mar. 17, 2016 USD ($)	Mar. 31, 2019 USD ($)	Feb. 28, 2019 USD ($) $ / shares	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Oct. 08, 2019	Oct. 10, 2018
Class of Stock [Line Items]
Distributions declared per common share (in dollars per share) | $ / shares		$ 3.50			$ 2.50					$ 2.50
Distributions paid per common share (in dollars per share) | $ / shares	$ 3.50			$ 2.50
Cash distributions paid | $	$ 427,700,000			$ 304,700,000						$ 1,200,000					$ 0
Preferred shares, of beneficial interest, shares outstanding (in shares) | shares													4,915,196	4,915,196
Common Shares
Class of Stock [Line Items]
Stock repurchase program, additional authorized amount | $			$ 150,000,000.0			$ 150,000,000.0	$ 150,000,000.0	$ 150,000,000.0
Stock repurchase program, period in force			12 months			12 months	12 months	12 months
Stock repurchase program, amount not utilized | $									$ 130,900,000		$ 81,000,000.0	$ 106,600,000
Number of shares repurchased (in shares) | shares													0	2,970,209	0
Stock repurchased and retired during period, price per share (in dollars per share) | $ / shares														$ 29.67
Redemption of shares | $						$ 19,100,000	$ 69,000,000.0							$ 88,100,000
Stock repurchase program, remaining authorized repurchase amount | $													$ 150,000,000.0
Stock repurchase program, number of shares surrendered (in shares) | shares													168,327	193,521	43,329
Common shares from conversion of preferred shares (in shares) | shares													2,857,203
Series D Preferred Stock
Class of Stock [Line Items]
Preferred shares dividend (in dollars per share) | $ / shares													$ 1.625
Initial conversion rate					0.480775											0.5813	0.5215
Initial conversion price per share (in dollars per share) | $ / shares													$ 43.01
Additional common shares (in shares) | shares													2,857,203
Liquidation preference (in dollars per share) | $ / shares													$ 25.00
Percentage of average closing market price of the entity's common stock based on which ratio for conversion of preferred shares into common shares is determined													98.00%
Purchase price as a percentage of liquidation preference													100.00%
Common shares from conversion of preferred shares (in shares) | shares													4,915,196