Distributions - Summary of Distributions Paid Including Activity in Plan as well as Limited Partnership Units Issued from Reinvestment of Unit Distributions (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends [Line Items]
Preferred Stockholders													$ 11,194	$ 12,390	$ 12,402
Common Stockholders													49,383	48,568	46,306
Limited Partnership Unitholders													$ 16,751	$ 16,642	$ 15,981
Common Stock Shares Issued (in shares)													228,498,000	430,462,000	572,928,000
Limited Partnership Units Issued (in shares)													51,579,000	60,936,000	107,433,000
4th Quarter
Dividends [Line Items]
Preferred Stockholders	$ 2,798				$ 3,531				$ 2,953
Common Stockholders	12,371				12,251				11,706
Limited Partnership Unitholders	$ 4,195				$ 4,173				$ 4,062
Common Stock Shares Issued (in shares)	117,368,000				104,558,000				216,476,000
Discounted Share Price (in usd per share)	$ 24.08				$ 52.84				$ 49.34				$ 24.08	$ 52.84	$ 49.34
Limited Partnership Units Issued (in shares)	23,370,000				13,747,000				13,867,000
Average Unit Price (in usd per share)	$ 24.35				$ 53.73				$ 50.20				$ 24.35	$ 53.73	$ 50.20
3rd Quarter
Dividends [Line Items]
Preferred Stockholders		$ 2,798				$ 2,953				$ 2,953
Common Stockholders		12,373				12,195				11,590
Limited Partnership Unitholders		$ 4,188				$ 4,166				$ 4,055
Common Stock Shares Issued (in shares)		14,525,000				105,753,000				201,500,000
Discounted Share Price (in usd per share)		$ 28.98				$ 53.66				$ 51.68
Limited Partnership Units Issued (in shares)		13,108,000				13,406,000				13,107,000
Average Unit Price (in usd per share)		$ 29.47				$ 54.56				$ 52.60
2nd Quarter
Dividends [Line Items]
Preferred Stockholders			$ 2,799				$ 2,953				$ 2,672
Common Stockholders			12,364				12,116				11,545
Limited Partnership Unitholders			$ 4,188				$ 4,155				$ 3,942
Common Stock Shares Issued (in shares)			12,627,000				99,804,000				85,202,000
Discounted Share Price (in usd per share)			$ 32.22				$ 51.38				$ 47.54
Limited Partnership Units Issued (in shares)			0				20,041,000				42,422,000
Average Unit Price (in usd per share)			$ 0				$ 51.99				$ 47.83
1st Quarter
Dividends [Line Items]
Preferred Stockholders				$ 2,799				$ 2,953				$ 3,824
Common Stockholders				12,275				12,006				11,465
Limited Partnership Unitholders				$ 4,180				$ 4,148				$ 3,922
Common Stock Shares Issued (in shares)				83,978,000				120,347,000				69,750,000
Discounted Share Price (in usd per share)				$ 48.59				$ 51.28				$ 52.71
Limited Partnership Units Issued (in shares)				15,101,000				13,742,000				38,037,000
Average Unit Price (in usd per share)				$ 49.40				$ 52.16				$ 53.03