INCOME TAXES - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective income tax rate reconciliation [Abstract]
Income taxes computed at the federal statutory rate	$ 37,914	$ 49,287	$ 44,270
Benefit of REIT status	(37,913)	(49,283)	(44,270)
Income taxes computed on income of Capstead's sole taxable REIT subsidiary	1	4	0
Change in net deferred income tax assets	(1)	(4)	1
Other	0	0	(1)
Income tax provision	$ 0	$ 0	$ 0