Schedule of Acquired Facilities and Purchase Price of the Facilities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Property	Sep. 30, 2011
Finite-Lived Intangible Assets [Line Items]
Number of Properties			14
Purchase Price	$ 106,185		$ 106,185
Cash Paid	105,137		105,137
Loan Assumed
Net Other Liabilities (Assets) Assumed	1,048		1,048
Land	19,466		19,466
Building, Equipment, and Improvements	84,791		84,791
In-Place Customers Leases			1,928
Closing Costs Expensed	1,075	2,913	2,382	3,048
Date Of Acquisition, 5/16/2012 [Member] | Florida [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			1
Date of Acquisition			May 16, 2012
Purchase Price	15,340		15,340
Cash Paid	15,163		15,163
Loan Assumed
Net Other Liabilities (Assets) Assumed	177		177
Land	2,960		2,960
Building, Equipment, and Improvements	12,077		12,077
In-Place Customers Leases			303
Closing Costs Expensed			516
Date Of Acquisition, 6/6/2012 [Member] | Illinois [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			2
Date of Acquisition			Jun. 06, 2012
Purchase Price	20,750		20,750
Cash Paid	20,304		20,304
Loan Assumed
Net Other Liabilities (Assets) Assumed	446		446
Land	3,871		3,871
Building, Equipment, and Improvements	16,486		16,486
In-Place Customers Leases			393
Closing Costs Expensed			537
Date Of Acquisition, 6/20/2012 [Member] | Virginia [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			1
Date of Acquisition			Jun. 20, 2012
Purchase Price	6,920		6,920
Cash Paid	6,884		6,884
Loan Assumed
Net Other Liabilities (Assets) Assumed	36		36
Land	911		911
Building, Equipment, and Improvements	5,862		5,862
In-Place Customers Leases			147
Closing Costs Expensed			254
Date Of Acquisition, 7/18/2012 [Member] | Georgia [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			1
Date of Acquisition			Jul. 18, 2012
Purchase Price	8,500		8,500
Cash Paid	8,442		8,442
Loan Assumed
Net Other Liabilities (Assets) Assumed	58		58
Land	1,560		1,560
Building, Equipment, and Improvements	6,766		6,766
In-Place Customers Leases			174
Closing Costs Expensed			40
Date Of Acquisition, 9/18/2012 [Member] | Florida [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			3
Date of Acquisition			Sep. 18, 2012
Purchase Price	15,957		15,957
Cash Paid	15,749		15,749
Loan Assumed
Net Other Liabilities (Assets) Assumed	208		208
Land	2,176		2,176
Building, Equipment, and Improvements	13,461		13,461
In-Place Customers Leases			320
Closing Costs Expensed			301
Date Of Acquisition, 9/18/2012 [Member] | Georgia [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			4
Date of Acquisition			Sep. 18, 2012
Purchase Price	26,883		26,883
Cash Paid	26,856		26,856
Loan Assumed
Net Other Liabilities (Assets) Assumed	27		27
Land	4,438		4,438
Building, Equipment, and Improvements	22,110		22,110
In-Place Customers Leases			335
Closing Costs Expensed			452
Date Of Acquisition, 9/19/2012 [Member] | North Carolina [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			1
Date of Acquisition			Sep. 19, 2012
Purchase Price	7,400		7,400
Cash Paid	7,374		7,374
Loan Assumed
Net Other Liabilities (Assets) Assumed	26		26
Land	2,337		2,337
Building, Equipment, and Improvements	4,900		4,900
In-Place Customers Leases			163
Closing Costs Expensed			213
Date Of Acquisition, 9/27/2012 [Member] | Illinois [Member]
Finite-Lived Intangible Assets [Line Items]
Number of Properties			1
Date of Acquisition			Sep. 27, 2012
Purchase Price	4,435		4,435
Cash Paid	4,365		4,365
Loan Assumed
Net Other Liabilities (Assets) Assumed	70		70
Land	1,213		1,213
Building, Equipment, and Improvements	3,129		3,129
In-Place Customers Leases			93
Closing Costs Expensed			$ 69