Condensed Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract]
Net income	$ 49,628,000	$ 63,018,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	12,653,000	8,768,000
Straight-line rental income	(2,325,000)	(2,762,000)
Non-cash interest income on construction loan	0	(781,000)
Loan and realty recoveries	(2,300,000)	99,000
Gain on sale of real estate	0	(3,348,000)
Net realized gains on sales of marketable securities	(30,000)	(9,899,000)
Share-based compensation	1,924,000	2,912,000
Change in fair value of interest rate swap agreement	0	922,000
Increase (Decrease) in Operating Capital [Abstract]
Deferred costs and other assets	596,000	67,000
Accounts payable and accrued expenses	(712,000)	(395,000)
Deferred income	(299,000)	253,000
Net cash provided by operating activities	63,735,000	58,656,000
Net Cash Provided by (Used in) Investing Activities [Abstract]
Investment in mortgage notes receivable	(5,797,000)	(6,567,000)
Collection of mortgage notes receivable	2,844,000	3,584,000
Investment in real estate properties	(77,740,000)	(24,935,000)
Investment in unconsolidated subsidiary	(8,309,000)	0
Payment of real estate purchase liability	(3,000,000)	0
Receipt of earnest money deposit	0	525,000
Proceeds from disposition of real estate properties	0	8,971,000
Proceeds from sales of marketable securities	125,000	12,862,000
Net cash used in investing activities	(91,877,000)	(5,560,000)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net change in borrowings under a revolving credit facility	(42,300,000)	(37,765,000)
Borrowings on term loan	120,000,000	50,000,000
Debt issuance costs	(753,000)	0
Principal payments on debt	0	(1,875,000)
Stock options exercised	(2,000)	199,000
Dividends paid to stockholders	(60,279,000)	(50,835,000)
Net cash used in financing activities	16,666,000	(40,276,000)
(Decrease) increase in cash and cash equivalents	(11,476,000)	12,820,000
Cash and cash equivalents, beginning of year	15,886,000	2,664,000
Cash and cash equivalents, end of year	4,410,000
Supplemental disclosure of cash flow information:
Interest Paid	2,129,000	1,781,000
Supplemental schedule of non-cash investing and financing activities:
Assumption of debt in real estate acquisition	19,250,000	0
Decrease in fair value of cash flow hedge	1,343,000	0
Earnest money deposit applied to sale of real estate	$ 0	$ 4,000,000