Consolidated Statement Of Changes In Equity - USD ($) $ in Thousands		Total		Parent [Member]	Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Parent at Dec. 31, 2013				$ 620,401
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2013					$ 5,648
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2013		$ 626,049
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
Net investment income	[1]	39,687
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions	[1]	6,610
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation	[1]	10,893
Net Income (Loss) Attributable to Parent		56,530	[1]	56,530
Net Income (Loss) Attributable to Noncontrolling Interest		660	[1]		660
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	[1]	57,190
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Proceeds from the issuance of shares	[2]	188,400		188,400
Shares issued in connection with incentive fee payment		309		309
Contributions from non-controlling interests		1,524			1,524
Dividends	[3]	(60,210)	[4]	(59,720)	(490)
Distributions to non-controlling interest		(1,099)			(1,099)
Adjustment to non-controlling interest		0		(486)	486
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs		(247)		(247)
Shares repurchased		0		0
Share-based LTIP awards		191		190	1
Net increase (decrease) in equity from transactions		128,868		128,446	422
Net increase (decrease) in equity		186,058		184,976	1,082
Stockholders' Equity Attributable to Parent at Sep. 30, 2014				805,377
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2014					6,730
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2014		812,107
Stockholders' Equity Attributable to Parent at Dec. 31, 2014		782,155		782,155
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2014		6,389			6,389
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2014		788,544
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
Net investment income		52,720
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions		19,470
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation		(35,622)
Net Income (Loss) Attributable to Parent		36,309		36,309
Net Income (Loss) Attributable to Noncontrolling Interest		259			259
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		36,568
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Proceeds from the issuance of shares	[2]	0		0
Shares issued in connection with incentive fee payment		0		0
Contributions from non-controlling interests		1,430			1,430
Dividends	[3]	(66,462)	[4]	(66,048)	(414)
Distributions to non-controlling interest		(1,410)			(1,410)
Adjustment to non-controlling interest		0		0	0
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs		0		0
Shares repurchased		(623)		(623)
Share-based LTIP awards		294		292	2
Net increase (decrease) in equity from transactions		(66,771)		(66,379)	(392)
Net increase (decrease) in equity		(30,203)		(30,070)	(133)
Stockholders' Equity Attributable to Parent at Sep. 30, 2015		752,085		$ 752,085
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2015		6,256			$ 6,256
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2015		$ 758,341

[1] Conformed to current period presentation.

[2] For the nine month period ended September 30, 2014 proceeds from the issuance of shares is net of an underwriters' discount of $3.0 million.

[3] For the nine month periods ended September 30, 2015 and 2014, dividends totaling $1.95 and $2.31, respectively, per common share and convertible unit outstanding, were declared and paid.

[4] 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.