Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	9 Months Ended	12 Months Ended
	Aug. 16, 2019	Feb. 07, 2019	Nov. 30, 2018	Mar. 31, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 31, 2019
Class of Stock [Line Items]
Purchase of OP units from non-controlling interest			$ 21,800			$ 0	$ 21,764	$ 0
Repurchase of shares of common stock (in shares)							75,100
Repurchase of shares of common stock			$ 1,100				$ 1,144
Average price per repurchased common share							$ 15.23
2009 Equity Incentive Plan
Class of Stock [Line Items]
Total unrecognized compensation cost expected to be recognized						$ 131
Total unrecognized compensation cost expected to be recognized, period for recognition						39 months
Total unrecognized compensation cost expected to be recognized, weighted average remaining vesting period						15 months
2009 Equity Incentive Plan | Non-Executive Director
Class of Stock [Line Items]
Compensation expense recognized						$ 450	$ 424	$ 453
Restricted stock awards during period (in shares)						27,665	27,697	25,006
2009 Equity Incentive Plan | Employees of the Manager and its Affiliates
Class of Stock [Line Items]
Compensation expense recognized						$ 72	$ 129	$ 138
Equity Distribution Agreement
Class of Stock [Line Items]
Equity distribution agreement, number of shares to sell				7,000,000
Series A Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, percentage rate						7.75%
Preferred stock, liquidation preference						$ 25.00
Preferred stock, price per share per annum						1.9375
Series B Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, price per share per annum						$ 1.9375
Preferred stock dividend rate						7.75%
Preferred stock redemption price (in usd per share)						$ 25.00
Series B Cumulative Redeemable Preferred Stock | LIBOR
Class of Stock [Line Items]
Preferred stock dividends basis spread on variable rate						5.18%
Series C Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, liquidation preference						$ 25.00
Preferred stock, price per share per annum						$ 1.875
Preferred stock dividend rate						7.50%
Preferred stock redemption price (in usd per share)						$ 25.00
Series C Cumulative Redeemable Preferred Stock | LIBOR
Class of Stock [Line Items]
Preferred stock dividends basis spread on variable rate						5.289%
Common Stock
Class of Stock [Line Items]
Equity distribution agreement, number of shares to sell				17,000,000
Number of shares issued during period (in shares)	14,000,000	16,100,000
Sale of stock, price (in USD per share)	$ 15.86	$ 15.73
Proceeds from issuance of common stock	$ 219,300	$ 249,500
Number of shares authorized to be repurchased (in shares)						18,163,982
Common Stock | 2009 Equity Incentive Plan
Class of Stock [Line Items]
Common stock options reserved for issuance									200,000
Common Stock | Equity Distribution Agreement
Class of Stock [Line Items]
Number of shares issued during period (in shares)						2,540,260
Proceeds from issuance of common stock						$ 40,100
Payments of stock issuance costs					$ 846