Consolidated Statement Of Changes In Equity - USD ($) $ in Thousands		Total		Parent [Member]	Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Parent at Dec. 31, 2014				$ 782,155
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2014					$ 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		66,176
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions		20,953
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation		(48,700)
Net Income (Loss) Attributable to Parent		38,089		38,089
Net Income (Loss) Attributable to Noncontrolling Interest		340			340
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		38,429
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Contributions from non-controlling interests		2,153			2,153
Dividends	[1]	(83,460)	[2]	(82,940)	(520)
Distributions to non-controlling interest		(1,468)			(1,468)
Adjustment to non-controlling interest		0		(6)	6
Shares repurchased		(5,639)		(5,639)
Share-based LTIP awards		393		390	3
Net increase (decrease) in equity from transactions		(88,021)		(88,195)	174
Net increase (decrease) in equity		(49,592)		(50,106)	514
Stockholders' Equity Attributable to Parent at Dec. 31, 2015				732,049
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2015					6,903
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2015		738,952
CHANGE IN SHAREHOLDERS’ EQUITY RESULTING FROM OPERATIONS
NET INVESTMENT INCOME		35,765
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions		(39,533)
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation		(11,934)
Net Income (Loss) Attributable to Parent		(16,007)		(16,007)
Net Income (Loss) Attributable to Noncontrolling Interest		305			305
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		(15,702)
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Contributions from non-controlling interests		5,552			5,552
Dividends	[1]	(65,148)	[2]	(64,735)	(413)
Distributions to non-controlling interest		(5,249)			(5,249)
Adjustment to non-controlling interest		0		(15)	15
Shares repurchased		(14,028)		(14,028)
Share-based LTIP awards		400		397	3
Net increase (decrease) in equity from transactions		(78,473)		(78,381)	(92)
Net increase (decrease) in equity		(94,175)		(94,388)	213
Stockholders' Equity Attributable to Parent at Dec. 31, 2016		637,661		637,661
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2016		7,116			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		35,168
Net realized gain (loss) on investments, financial derivatives, and foreign currency transactions		(10,804)
Change in net unrealized gain (loss) on investments, financial derivatives, and foreign currency translation		11,600
Net Income (Loss) Attributable to Parent		33,981		33,981
Net Income (Loss) Attributable to Noncontrolling Interest		1,983			1,983
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		35,964
CHANGE IN EQUITY RESULTING FROM TRANSACTIONS
Contributions from non-controlling interests		20,707			20,707
Dividends	[1]	(57,636)	[2]	(57,263)	(373)
Distributions to non-controlling interest		(8,594)			(8,594)
Adjustment to non-controlling interest		0		(21)	21
Shares repurchased		(14,642)		(14,642)
Share-based LTIP awards		385		383	2
Net increase (decrease) in equity from transactions		(59,780)		(71,543)	11,763
Net increase (decrease) in equity		(23,816)		(37,562)	13,746
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

[1] For the years ended December 31, 2017, 2016, and 2015, dividends totaling $1.76, $1.95, and $2.45, 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.