Consolidated Statement Of Changes In Equity (USD $) In Thousands, unless otherwise specified		Total		Parent [Member]	Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2011		$ 370,916
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2011					0
Stockholders' Equity Attributable to Parent at Dec. 31, 2011				370,916
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
Net investment income		20,514
Net realized gain (loss) on investments and financial derivatives		(18,126)
Change in net unrealized gain (loss) on investments and financial derivatives		69,972
Net Income (Loss) Attributable to Parent		72,360		72,360
Net Income (Loss) Attributable to Noncontrolling Interest		0			0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		72,360
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Proceeds from the issuance of shares		88,142		88,142
Shares issued in connection with incentive fee payment		231		231
Noncontrolling Interest, Increase from Equity Issuance or Sale of Parent Equity Interest		0			0
Dividends	[1]	(32,766)	[2]	(32,766)	0
Offering costs		(322)		(322)
Share-based LTIP awards		89		89	0
Net increase (decrease) in equity from transactions		55,374		55,374	0
Net increase in equity		127,734		127,734	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2012		498,650
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2012					0
Stockholders' Equity Attributable to Parent at Sep. 30, 2012				498,650
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2012		506,355
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2012		0			0
Stockholders' Equity Attributable to Parent at Dec. 31, 2012		506,355		506,355
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
Net investment income		37,144
Net realized gain (loss) on investments and financial derivatives		22,552
Change in net unrealized gain (loss) on investments and financial derivatives		4,578
Net Income (Loss) Attributable to Parent		63,662		63,662
Net Income (Loss) Attributable to Noncontrolling Interest		612			612
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		64,274
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Proceeds from the issuance of shares		125,600		125,600
Shares issued in connection with incentive fee payment		1,058		1,058
Noncontrolling Interest, Increase from Equity Issuance or Sale of Parent Equity Interest		4,664			4,664
Dividends	[1]	(72,016)	[2]	(71,368)	(648)
Offering costs		(262)		(262)
Share-based LTIP awards		129		128	1
Net increase (decrease) in equity from transactions		59,173		55,156	4,017
Net increase in equity		123,447		118,818	4,629
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2013		629,802
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2013		4,629			4,629
Stockholders' Equity Attributable to Parent at Sep. 30, 2013		$ 625,173		$ 625,173

[1] For the nine month periods ended September 30, 2013 and 2012, dividends totaling $3.06 and $1.80, 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.