Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 81,132	$ 69,421	$ 64,229
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	11,992	11,203	8,621
Straight-line rental income	(3,778)	(3,140)	(627)
Non-cash interest income on construction loan	(1,082)	(298)
Loan and realty recoveries	(99)	(573)	(1,077)
Gain on sale of real estate	(3,348)	(2,004)
Net realized gains and recoveries on sales of marketable securities	(9,899)		(2,403)
Share-based compensation	3,087	2,368	853
Impairment of real estate assets in discontinued operations			25
Changes in operating assets and liabilities:
Accounts receivable	(713)	(73)	174
Deferred costs and other assets	(745)	(570)	102
Accounts payable and accrued expenses	95	634	(1,605)
Deferred income	212	576	770
Net cash provided by operating activities	76,854	77,544	69,062
Cash flows from investing activities:
Investment in mortgage notes receivable	(6,566)	(12,422)	(4,501)
Collection of mortgage notes receivable	4,540	9,482	19,630
Investment in real estate properties	(75,806)	(98,736)	(81,569)
Receipt of earnest money deposit	525	3,325	150
Proceeds from disposition of real estate properties	8,971	6,247	175
Acquisition of marketable securities			(274)
Proceeds from sales of marketable securities	12,862	75	11,261
Net cash used in investing activities	(55,474)	(92,029)	(55,128)
Cash flows from financing activities:
Net change in borrowings under a revolving credit facility	59,535	37,765
Borrowings on term loan	50,000
Principal payments on debt	(50,000)		(3,987)
Stock options exercised	200	183	78
Dividends paid to stockholders	(67,893)	(66,517)	(64,549)
Net cash used in financing activities	(8,158)	(28,569)	(68,458)
(Decrease) increase in cash and cash equivalents	13,222	(43,054)	(54,524)
Cash and cash equivalents, beginning of year	2,664	45,718	100,242
Cash and cash equivalents, end of year	15,886	2,664	45,718
Supplemental disclosure of cash flow information:
Interest paid	3,353	1,061	91
Supplemental schedule of non-cash investing and financing activities:
Settlement of mortgage note by real estate acquisition (Note 8)		22,936
Cash withheld at closing of real estate acquisition (Note 8)	5,478	1,000	3,000
Discount [Member]
Supplemental schedule of non-cash investing and financing activities:
Discount on Mortgage Note Receivable Purchased	$ 204		$ 1,132