Stock Transactions and Unit Redemptions - Unit Redemption and Share Repurchase Activity (Detail) - USD ($)	1 Months Ended			3 Months Ended
	Mar. 31, 2016	Feb. 29, 2016	Jan. 31, 2016	Mar. 31, 2016
Stock Transactions, Parenthetical Disclosures [Abstract]
Redemptions, Number of Units				775,791
Repurchases, Number of Shares	217,590	6,683,611	285,845	7,187,046
Total Redemptions and Repurchases, Number of Units and Shares				7,962,837
Redemptions, Average Price Paid per Unit				$ 8.59
Repurchases, Average Price Paid per Share	$ 9.09	$ 8.69	$ 9.09	8.72
Total Redemptions and Repurchases, Average Price Paid per Unit or Share				$ 8.71
Total Redemptions and Repurchases, Approximate Dollar Value of Units and Shares That May Yet Be Redeemed/Purchased Under the Plan	$ 225,060,546			$ 225,060,546