Consolidated Statement Of Changes In Equity - USD ($) $ in Thousands		Total		Parent [Member]	Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Parent at Dec. 31, 2016				$ 637,661
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2016					$ 7,116
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2016		$ 644,777
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
NET INVESTMENT INCOME		20,207
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions		(6,178)
Change in net unrealized gain (loss) on investments, other secured borrowings, financial derivatives, and foreign currency translation		7,142
Net Income (Loss) Attributable to Parent		20,342		20,342
Net Income (Loss) Attributable to Noncontrolling Interest		829			829
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		21,171
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Contributions from non-controlling interests		11,321			11,321
Dividends	[1]	(29,579)	[2]	(29,388)	(191)
Distributions to non-controlling interest		(8,050)			(8,050)
Adjustment to non-controlling interest		0		(4)	4
Shares repurchased		(2,868)		(2,868)
Share-based LTIP awards		189		188	1
Net increase (decrease) in equity from transactions		(28,987)		(32,072)	3,085
Net increase (decrease) in equity		(7,816)		(11,730)	3,914
Stockholders' Equity Attributable to Parent at Jun. 30, 2017				625,931
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2017					11,030
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2017		636,961
Stockholders' Equity Attributable to Parent at Dec. 31, 2017		600,099		600,099
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2017		20,862			20,862
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2017		620,961
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
NET INVESTMENT INCOME		21,234
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions		11,708
Change in net unrealized gain (loss) on investments, other secured borrowings, financial derivatives, and foreign currency translation		10,566
Net Income (Loss) Attributable to Parent		42,232		42,232
Net Income (Loss) Attributable to Noncontrolling Interest		1,276			1,276
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		43,508
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Contributions from non-controlling interests		2,165			2,165
Dividends	[1]	(25,501)	[2]	(25,327)	(174)
Distributions to non-controlling interest		(10,457)			(10,457)
Adjustment to non-controlling interest		0		(35)	35
Shares repurchased		(17,593)		(17,593)
Share-based LTIP awards		192		191	1
Net increase (decrease) in equity from transactions		(51,194)		(42,764)	(8,430)
Net increase (decrease) in equity		(7,686)		(532)	(7,154)
Stockholders' Equity Attributable to Parent at Jun. 30, 2018		599,567		$ 599,567
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2018		13,708			$ 13,708
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2018		$ 613,275

[1] For the six-month periods ended June 30, 2018 and 2017, dividends totaling $0.82 and $0.90, respectively, per common share and convertible unit outstanding, were declared and paid.

[2] The Company pays quarterly dividends in arrears, so a portion of the dividends paid in each calendar year relate to the prior year's earnings.