Common and Preferred Stock (Details) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended							8 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($) shares	Jan. 31, 2021 USD ($) shares	Apr. 30, 2020 USD ($) shares	Dec. 31, 2021 $ / shares	Sep. 30, 2021 USD ($) $ / shares shares	Mar. 31, 2021 shares	Sep. 30, 2020 shares	Jun. 30, 2020 shares	Mar. 31, 2020 USD ($) shares	Dec. 31, 2019 shares	Dec. 31, 2020 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	May 31, 2021 shares	Apr. 30, 2021 shares	Feb. 28, 2021 USD ($)	Jul. 31, 2019 USD ($)
Class of Stock [Line Items]
Common stock, shares authorized	180,000,000					180,000,000						90,000,000	180,000,000		90,000,000	180,000,000	90,000,000
Proceeds from common stock offerings, net | $													$ 650,859	$ 629,586
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.0001					$ 0.0001						$ 0.0001	$ 0.0001		$ 0.0001
Preferred stock, shares authorized	4,000,000					4,000,000						4,000,000	4,000,000		4,000,000
Proceeds from Series A preferred stock offering, net | $													$ 170,285
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding	7,000					7,000						0	7,000		0
Preferred stock, dividend rate, percentage	4.25%
Preferred Stock, Liquidation Preference, Value | $	$ 25,000					$ 25,000							$ 25,000
Number of Shares Exchanged, Underlying Depository Shares	7,000
Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share | $ / shares	$ 25.00					$ 25.00							$ 25.00
Cash dividends declared per depositary share of Series A preferred stock | $ / shares	0.041
Preferred Stock, Redemption Price Per Share | $ / shares	$ 25.00					$ 25.00							$ 25.00
Redeemable Preferred Stock [Member] | Scenario, Plan [Member]
Class of Stock [Line Items]
Cash dividends declared per depositary share of Series A preferred stock | $ / shares					$ 0.08854
Preferred stock, dividends declared per annum (in dollars per share) | $ / shares					$ 1.0625
Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares authorized				2,875,000
Issuance of common stock, net of issuance costs (in shares)						885,912	4,028,410	1,515,000	6,851,695	1,400,251
Proceeds from common stock offerings, net | $				$ 170,400
Common Stock [Member] | Forward Sale Agreement [Member]
Class of Stock [Line Items]
Common stock, shares authorized		4,600,000	3,450,000	6,166,666
Proceeds from common stock offerings, net | $		$ 327,000										$ 354,600
At-Market Equity Program [Member] | Common Stock [Member]
Class of Stock [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares										3,169,754
At-Market Equity Program Two [Member] | Common Stock [Member]
Class of Stock [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares											2,003,118
Proceeds from common stock offerings, net | $															$ 359,500
Value Of Equity Instruments To Be Issued | $																			$ 400,000
At-Market Equity Program Three [Member] | Common Stock [Member]
Class of Stock [Line Items]
Value Of Equity Instruments To Be Issued | $	$ 0					$ 0							$ 0
At-Market Equity Program Four [Member] | Common Stock [Member]
Class of Stock [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares															3,334,056
Issuance of common stock, net of issuance costs (in shares)													1,628,772		204,074
Proceeds from common stock offerings, net | $													$ 102,800		$ 12,500
Value Of Equity Instruments To Be Issued | $										$ 400,000
At-Market Equity Program Five [Member] | Common Stock [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)													0
Value Of Equity Instruments To Be Issued | $																		$ 500,000
Over-Allotment Option [Member] | Series A Preferred Stock [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)	7,000
Stockholders' Equity Note, Stock Split, Conversion Ratio	0.001
Proceeds from Series A preferred stock offering, net | $	$ 170,300
Over-Allotment Option [Member] | Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs (in shares)	7,000,000
Over-Allotment Option [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares authorized				375,000
Over-Allotment Option [Member] | Common Stock [Member] | Forward Sale Agreement [Member]
Class of Stock [Line Items]
Common stock, shares authorized		600,000	450,000
Common Stock [Member] | Forward Sale Agreement [Member]
Class of Stock [Line Items]
Proceeds from common stock offerings, net | $			$ 221,400
Common Stock [Member] | At-Market Equity Program Four [Member]
Class of Stock [Line Items]
Value Of Equity Instruments To Be Issued | $	$ 0					$ 0							$ 0
Common Stock [Member] | At-Market Equity Program Five [Member]
Class of Stock [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares													1,918,130