Consolidated Statements Of Income - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Rental income	$ 265,127,000	$ 232,353,000	$ 214,407,000
Interest income from mortgage and other notes	13,134,000	13,805,000	10,206,000
Investment income and other	398,000	2,302,000	4,335,000
Revenues	278,659,000	248,460,000	228,948,000
Expenses:
Depreciation	67,173,000	59,525,000	53,123,000
Interest expense	46,324,000	43,108,000	37,629,000
Legal expense	494,000	422,000	464,000
Franchise, excise and other taxes	960,000	1,009,000	985,000
General and administrative	12,217,000	9,773,000	10,519,000
Loan and realty losses (recoveries), net	0	(15,856,000)	491,000
Total operating expenses	127,168,000	129,693,000	102,229,000
Income before equity-method investee, tax benefit (expense), investment and other gains, discontinued operations and noncontrolling interest	151,491,000	118,767,000	126,719,000
Income from equity-method investee	0	1,214,000	1,767,000
Loss on convertible note retirement	(2,214,000)	0	0
Income tax benefit (expense) of taxable REIT subsidiary	0	(749,000)	707,000
Investment and other gains	10,088,000	35,912,000	24,655,000
Discontinued operations
Net income	159,365,000	152,716,000	150,314,000
Less: net income attributable to noncontrolling interest	0	(1,176,000)	(1,452,000)
Net income attributable to common stockholders	$ 159,365,000	$ 151,540,000	$ 148,862,000
Weighted average common shares outstanding:
Basic	40,894,219	39,013,412	37,604,594
Diluted	41,151,453	39,155,380	37,644,171
Basic:
Net income per common share attributable to common stockholders	$ 3.90	$ 3.88	$ 3.96
Diluted:
Net income per common share attributable to common stockholders	$ 3.87	$ 3.87	$ 3.95