Condensed Consolidated Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Distributions in Excess of Net Income [Member]	Stockholders' Investment [Member]	Nonredeemable Noncontrolling Interests [Member]
Beginning balance at Dec. 31, 2011
Net Income (Loss) in Statement on Equity	$ 49,922	$ 0	$ 0	$ 0	$ 0	$ 45,728	$ 45,728	$ 4,194
Net Income (Loss) Attributable to Parent	45,728
Common stock issued pursuant to:
Director stock grants	540	0	72	468	0	0	540	0
Stock option exercises	0	0	0	0	0	0	0	0
Restricted stock grants, net of amounts withheld for income taxes	(207)	0	452	(659)	0	0	(207)	0
Amortization of stock options and restricted stock, net of forfeitures	2,244	0	(136)	2,380	0	0	2,244	0
Distributions to nonredeemable noncontrolling interests	(15,286)	0	0	0	0	0	0	(15,286)
Contributions from Nonredeemable Noncontrolling Interest	1,300	0	0	0	0	0	0	1,300
Preferred Stock Redemption	0
Change in fair value of redeemable noncontrolling interests	0	0	0	0	0	0	0	0
Cash preferred dividends paid	(12,907)	0	0	0	0	(12,907)	(12,907)	0
Cash common dividends paid	(18,748)	0	0	0	0	(18,748)	(18,748)	0
Ending balance at Dec. 31, 2012	642,953	169,602	107,660	690,024	(86,840)	(260,104)	620,342	22,611
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	126,761	0	0	0	0	121,761	121,761	5,000
Net Income (Loss) Attributable to Parent	121,761
Common stock issued pursuant to:
Director stock grants	544	0	50	494	0	0	544	0
Restricted stock grants, net of amounts withheld for income taxes	(1,179)	0	30	(1,209)	0	0	(1,179)	0
Amortization of stock options and restricted stock, net of forfeitures	1,898	0	(42)	1,940	0	0	1,898	0
Distributions to nonredeemable noncontrolling interests	(26,040)	0	0	0	0	0	0	(26,040)
Preferred Stock Redemption	(74,827)
Cash preferred dividends paid	(10,008)	0	0	0	0	(10,008)	(10,008)	0
Cash common dividends paid	(27,192)	0	0	0	0	(27,192)	(27,192)	0
Ending balance at Dec. 31, 2013	1,458,972	94,775	193,236	1,420,951	(86,840)	(164,721)	1,457,401	1,571
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	53,008	0	0	0	0		52,004	1,004
Net Income (Loss) Attributable to Parent	52,004
Common stock issued pursuant to:
Director stock grants	653	0	55	598	0	0	653	0
Stock option exercises	(278)	0	48	(326)	0	0	(278)	0
Common stock offering, net of issuance costs	321,896	0	26,700	295,196	0	0	321,896	0
Restricted stock grants, net of amounts withheld for income taxes	(925)	0	53	(978)	0	0	(925)	0
Amortization of stock options and restricted stock, net of forfeitures	1,992	0	(9)	2,001	0	0	1,992	0
Distributions to nonredeemable noncontrolling interests	(2,575)	0	0	0	0	0	0	(2,575)
Preferred Stock Redemption	(94,775)	(94,775)	0	3,530	0	(3,530)	(94,775)	0
Cash preferred dividends paid	(2,955)	0	0	0	0	(2,955)	(2,955)	0
Cash common dividends paid	(61,555)	0	0	0	0	(61,555)	(61,555)	0
Ending balance at Dec. 31, 2014	$ 1,673,458	$ 0	$ 220,083	$ 1,720,972	$ (86,840)	$ (180,757)	$ 1,673,458	$ 0