Life Storage Inc - Registered Shares (LSI) 10-Q 4 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 24, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	SSS
Entity Registrant Name	SOVRAN SELF STORAGE INC
Entity Central Index Key	944314
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		35,562,772

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Investment in storage facilities:
Land	$433,026	$397,642
Building, equipment, and construction in progress	1,883,571	1,780,341
Real estate investment property, at cost, total	2,316,597	2,177,983
Less: accumulated depreciation	-424,764	-411,701
Investment in storage facilities, net	1,891,833	1,766,282
Cash and cash equivalents	10,312	8,543
Accounts receivable	5,745	5,758
Receivable from unconsolidated joint ventures	728	583
Investment in unconsolidated joint ventures	57,659	57,803
Prepaid expenses	6,976	6,533
Other assets	8,925	9,298
Total Assets	1,982,178	1,854,800
Liabilities
Line of credit	63,000	49,000
Term notes	750,000	750,000
Accounts payable and accrued liabilities	33,324	43,551
Deferred revenue	7,679	7,290
Fair value of interest rate swap agreements	17,318	13,341
Mortgages payable	2,095	2,127
Total Liabilities	873,416	865,309
Noncontrolling redeemable Operating Partnership Units at redemption value	16,987	13,622
Shareholders' Equity
Common stock $.01 par value, 100,000,000 shares authorized, 35,562,772 shares outstanding at March 31, 2015 (34,105,955 at December 31, 2014)	367	353
Additional paid-in capital	1,307,653	1,183,388
Dividends in excess of net income	-172,078	-167,692
Accumulated other comprehensive loss	-16,992	-13,005
Treasury stock at cost, 1,171,886 shares	-27,175	-27,175
Total Shareholders' Equity	1,091,775	975,869
Total Liabilities and Shareholders' Equity	$1,982,178	$1,854,800

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares outstanding	35,562,772	34,105,955
Treasury stock at cost, shares	1,171,886	1,171,886

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenues
Rental income	$78,886	$69,953
Other operating income	6,522	5,504
Total operating revenues	85,408	75,457
Expenses
Property operations and maintenance	20,559	18,484
Real estate taxes	8,920	8,066
General and administrative	9,406	8,536
Acquisition costs	582	2,778
Operating leases of storage facilities	683	1,997
Depreciation and amortization	14,181	11,942
Total operating expenses	54,331	51,803
Income from operations	31,077	23,654
Other income (expenses)
Interest expense	-9,161	-7,343
Interest income	2	6
Loss on sale of storage facility	-7
Equity in income of joint ventures	646	458
Net income	22,557	16,775
Net income attributable to noncontrolling interest	-106	-102
Net income attributable to common shareholders	$22,451	$16,673
Earnings per common share attributable to common shareholders - basic	$0.65	$0.51
Earnings per common share attributable to common shareholders - diluted	$0.65	$0.51
Common shares used in basic earnings per share calculation	34,329,768	32,383,996
Common shares used in diluted earnings per share calculation	34,554,871	32,538,429
Dividends declared per common share	$0.75	$0.68

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$22,557	$16,775
Other comprehensive income:
Change in fair value of derivatives net of reclassification to interest expense	-3,987	-1,929
Total comprehensive income	18,570	14,846
Comprehensive income attributable to noncontrolling interest	-87	-90
Comprehensive income attributable to common shareholders	$18,483	$14,756

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating Activities
Net income	$22,557	$16,775
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,181	11,937
Amortization of deferred financing fees	296	195
Loss on sale of storage facility	7
Equity in income of joint ventures	-646	-458
Distributions from unconsolidated joint ventures	1,017	618
Non-vested stock earned	1,612	1,223
Stock option expense	36	36
Changes in assets and liabilities (excluding the effects of acquisitions):
Accounts receivable	13	356
Prepaid expenses	-443	-1,588
(Advances to) receipts from joint ventures	-145	72
Accounts payable and other liabilities	-7,887	-10,794
Deferred revenue	342	224
Net cash provided by operating activities	30,940	18,596
Investing Activities
Acquisitions of storage facilities	-134,040	-89,101
Improvements, equipment additions, and construction in progress	-5,335	-4,631
Net proceeds from the sale of storage facility	711
Investment in unconsolidated joint ventures	-285
Property deposit	-1,095	-1,161
Net cash used in investing activities	-140,044	-94,893
Financing Activities
Net proceeds from sale of common stock	122,631	29,360
Proceeds from line of credit	144,000	92,000
Repayments of line of credit	-130,000	-26,000
Financing costs		-50
Dividends paid-common stock	-25,609	-22,111
Distributions to noncontrolling interest holders	-117	-135
Mortgage principal payments	-32	-31
Net cash provided by financing activities	110,873	73,033
Net increase (decrease) in cash	1,769	-3,264
Cash at beginning of period	8,543	9,524
Cash at end of period	10,312	6,260
Supplemental cash flow information
Cash paid for interest, net of interest capitalized	$5,307	$6,140

Basis_of_Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	1	BASIS OF PRESENTATION
	The accompanying unaudited financial statements of Sovran Self Storage, Inc. have been prepared in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three month period ended March 31, 2015 are not necessarily indicative of the results that may be expected for the year ending December 31, 2015.
	Reclassification: Certain amounts from the 2014 financial statements have been reclassified to conform with the current year presentation. See Note 15.

Organization

Organization	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Organization	2	ORGANIZATION
	Sovran Self Storage, Inc. (the “Company,” “We,” “Our,” or “Sovran”), a self-administered and self-managed real estate investment trust (a “REIT”), was formed on April 19, 1995 to own and operate self-storage facilities throughout the United States. On June 26, 1995, the Company commenced operations effective with the completion of its initial public offering. At March 31, 2015, we had an ownership interest in, leased, and/or managed 521 self-storage properties in 25 states under the name Uncle Bob’s Self Storage ®. Among our 521 self-storage properties are 39 properties that we manage for an unconsolidated joint venture (Sovran HHF Storage Holdings LLC) of which we are a 20% owner, 30 properties that we manage for an unconsolidated joint venture (Sovran HHF Storage Holdings II LLC) of which we are a 15% owner, and 19 properties that we manage and have no ownership interest. Approximately 40% of the Company’s revenue is derived from stores in the states of Texas and Florida. In addition, approximately 12% of the Company’s revenue is derived from the Houston, Texas market.
	All of the Company’s assets are owned by, and all its operations are conducted through, Sovran Acquisition Limited Partnership (the “Operating Partnership”). Sovran Holdings, Inc., a wholly-owned subsidiary of the Company (the “Subsidiary”), is the sole general partner of the Operating Partnership; the Company is a limited partner of the Operating Partnership, and through its ownership of the Subsidiary and its limited partnership interest controls the operations of the Operating Partnership, holding a 99.5% ownership interest therein as of March 31, 2015. The remaining ownership interests in the Operating Partnership (the “Units”) are held by certain former owners of assets acquired by the Operating Partnership subsequent to its formation.
	We consolidate all wholly owned subsidiaries. Partially owned subsidiaries and joint ventures are consolidated when we control the entity. Our consolidated financial statements include the accounts of the Company, the Operating Partnership, Uncle Bob’s Management, LLC (the Company’s taxable REIT subsidiary), Locke Sovran I, LLC (a wholly-owned subsidiary), and Locke Sovran II, LLC (a wholly-owned subsidiary). All intercompany transactions and balances have been eliminated. Investments in joint ventures that we do not control but for which we have significant influence over are accounted for using the equity method.
	Included in the consolidated balance sheets are noncontrolling redeemable operating partnership units. These interests are presented in the “mezzanine” section of the consolidated balance sheet because they do not meet the functional definition of a liability or equity under current accounting literature. These represent the outside ownership interests of the limited partners in the Operating Partnership. At March 31, 2015, there were 178,866 noncontrolling redeemable operating partnership Units outstanding (155,484 at December 31, 2014). These unitholders are entitled to receive distributions per unit equivalent to the dividends declared per share on the Company’s common stock. The Operating Partnership is obligated to redeem each of these limited partnership Units in the Operating Partnership at the request of the holder thereof for cash equal to the fair market value of a share of the Company’s common stock, at the time of such redemption, provided that the Company at its option may elect to acquire any such Unit presented for redemption for one common share or cash. The Company accounts for these noncontrolling redeemable Operating Partnership Units under the provisions of EITF D-98, “Classification and Measurement of Redeemable Securities” which was codified in FASB ASC Topic 480-10-S99. The application of the FASB ASC Topic 480-10-S99 accounting model requires the noncontrolling interest to follow normal noncontrolling interest accounting and then be marked to redemption value at the end of each reporting period if higher (but never adjusted below that normal noncontrolling interest accounting amount). The offset to the adjustment to the carrying amount of the noncontrolling redeemable Operating Partnership Units is reflected in dividends in excess of net income. Accordingly, in the accompanying consolidated balance sheet, noncontrolling redeemable Operating Partnership Units are reflected at redemption value at March 31, 2015 and December 31, 2014, equal to the number of Units outstanding multiplied by the fair market value of the Company’s common stock at that date. Redemption value exceeded the value determined under the Company’s historical basis of accounting at those dates.
	(dollars in thousands)		Three Months
			Ended
			Mar. 31, 2015
	Beginning balance noncontrolling redeemable Operating Partnership Units		$	13,622
	Issuance of Operating Partnership Units			2,148
	Net income attributable to noncontrolling interests – consolidated joint venture			106
	Distributions			(117	)
	Adjustment to redemption value			1,228
	Ending balance noncontrolling redeemable Operating Partnership Units		$	16,987
	In March 2015 the Operating Partnership issued 23,382 Units with a fair market value of $2.1 million to acquire one self-storage property. The fair value of the Units on the date of issuance was determined based upon the fair market value of the Company’s common stock on that date.

Stock_Based_Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	3	STOCK BASED COMPENSATION
	The Company accounts for stock-based compensation under the provisions of ASC Topic 718, “Compensation—Stock Compensation”. The Company recognizes compensation cost in its financial statements for all share based payments granted, modified, or settled during the period. For awards with graded vesting, compensation cost is recognized on a straight-line basis over the related vesting period.
	For the three months ended March 31, 2015 and 2014, the Company recorded compensation expense (included in general and administrative expense) of $36,000 and $36,000, respectively, related to stock options and $1,612,000 and $1,193,000, respectively, related to amortization of non-vested stock grants.
	During the three months ended March 31, 2015 and 2014, employees and directors exercised 9,500 and 1,500 stock options respectively, and 5,234 and 9,880 shares of non-vested stock, respectively, vested.

Investment_in_Storage_Faciliti

Investment in Storage Facilities	3 Months Ended
	Mar. 31, 2015
Real Estate [Abstract]
Investment in Storage Facilities	4	INVESTMENT IN STORAGE FACILITIES
	The following summarizes our activity in storage facilities during the three months ended March 31, 2015.
	(dollars in thousands)
	Cost:
	Beginning balance		$	2,177,983
	Acquisition of storage facilities			134,043
	Improvements and equipment additions			5,242
	Net increase in construction in progress			157
	Dispositions			(828	)
	Ending balance		$	2,316,597
	Accumulated Depreciation:
	Beginning balance		$	411,701
	Depreciation expense during the period			13,172
	Dispositions			(109	)
	Ending balance		$	424,764
	The four facilities acquired in Connecticut and New York on February 2, 2015 had been leased by the Company since November 1, 2013. The acquisitions of these four stores were accounted for as asset acquisitions. The cost of these four stores was assigned to their land, building, equipment and improvements components based upon their fair values. The assets and liabilities of the other two acquired storage facilities, which primarily consist of tangible and intangible assets, are measured at fair value on the date of acquisition in accordance with the principles of FASB ASC Topic 820, “Fair Value Measurements and Disclosures.” The purchase price of the six facilities has been assigned as follows:
	(dollars in thousands)										Consideration paid							Acquisition Date Fair Value
	State		Number of			Date of			Purchase		Cash Paid		Value of		Net Other			Land		Building,		In-Place		Closing
			Properties			Acquisition			Price				Operating		Liabilities					Equipment, and		Customer		Costs
													Partnership		(Assets)					Improvements		Leases		Expensed
													Units Issued		Assumed
	2015
	Connecticut			2			2/2/15		$	61,116	$	62,377	$	—	$	(1,261	)	$	19,389	$	41,727	$	—	$	—
	New York			2			2/2/15			57,900		59,103		—		(1,203	)		10,084		47,816		—		—
	Illinois			1			2/5/15			6,800		6,652		—		148			2,579		4,066		155		273
	Illinois			1			3/9/15			8,382		6,158		2,148		76			1,658		6,724		—		309
	Total acquired 2015			6					$	134,198	$	134,290	$	2,148	$	(2,240	)	$	33,710	$	100,333	$	155	$	582
	All of the properties acquired were purchased from unrelated third parties. The operating results of the four facilities which had been leased since November 1, 2013 have been included in the Company’s operations since that date. The operating results of the two facilities acquired in Illinois have been included in the Company’s operations since the respective acquisition dates. Of the $134.3 million paid at closing for the properties acquired during the three months ended
	March 31, 2015, $250,000 represented deposits that were paid in 2014 when certain of these properties originally went under contract. Non-cash investing activities during the three months ended March 31, 2015 include the issuance of $2.1 million in Operating Partnership Units, the assumption of $0.2 million of other net liabilities and $2.4 million for the settlement of a straight-line rent liability in connection with the acquisition of self-storage facilities.
	The Company measures the fair value of in-place customer lease intangible assets based on the Company’s experience with customer turnover. The Company amortizes in-place customer leases on a straight-line basis over 12 months (the estimated future benefit period). In-place customer leases are included in other assets on the Company’s balance sheet as follows:
	(Dollars in thousands)		Mar. 31,			Dec. 31,
			2015			2014
	In-place customer leases		$	19,927		$	19,867
	Accumulated amortization			(18,645	)		(17,663	)
	Net carrying value at the end of period		$	1,282		$	2,204
	Amortization expense related to in-place customer leases was $1.0 million and $0.7 million for the three months ended March 31, 2015 and 2014, respectively. The Company expects to record $2.3 million and $13,000 of amortization expense for the years ended December 31, 2015 and 2016, respectively.
	Property Dispositions
	During the three months ended March 31, 2015 the Company sold a non-strategic property purchased in May 2014 with a carrying value of $698,000 and received cash proceeds of approximately $691,000, resulting in a $7,000 loss on sale. The following table summarizes the revenues and expenses up to the date of sale of the property sold in 2015 that are included in the Company’s consolidated statements of operations for 2015 and 2014.
	(Dollars in thousands)		Jan. 31, 2015			Jan. 31, 2014
			to			to
			Mar. 31, 2015			Mar. 31, 2014
	Total revenues		$	40		$	—
	Property operations and maintenance expense			(16	)		—
	Real estate tax expense			(5	)		—
	Depreciation and amortization expense			(9	)		—
	Loss on sale of storage facilities			(7	)		—
			$	3		$	—

Unsecured_Line_of_Credit_and_T

Unsecured Line of Credit and Term Notes	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Unsecured Line of Credit and Term Notes	5	UNSECURED LINE OF CREDIT AND TERM NOTES
	Borrowings outstanding on our unsecured line of credit and term notes are as follows:
	(Dollars in thousands)		Mar. 31,		Dec. 31,
			2015		2014
	Revolving line of credit borrowings		$	63,000	$	49,000
	Term note due April 13, 2016			150,000		150,000
	Term note due June 4, 2020			325,000		325,000
	Term note due August 5, 2021			100,000		100,000
	Term note due April 8, 2024			175,000		175,000
	Total term notes payable		$	750,000	$	750,000
	On December 10, 2014, the Company amended its existing unsecured credit agreement. As part of the amended agreement, the Company increased its revolving credit limit from $175 million to $300 million. The interest rate on the revolving credit facility bears interest at a variable rate equal to LIBOR plus a margin based on the Company’s credit rating (at March 31, 2015 the margin is 1.30%), and requires a 0.20% facility fee. The amended agreement also reduced the interest rate on the $325 million unsecured term note maturing June 4, 2020, with the term note bearing interest at LIBOR plus a margin based on the Company’s credit rating (at March 31, 2015 the margin is 1.40%). The interest rate at March 31, 2015 on the Company’s line of credit was approximately 1.48% (1.46% at December 31, 2014). At March 31, 2015, there was $237 million available on the unsecured line of credit. The revolving line of credit has a maturity date of December 10, 2019. The amended agreement also provides for an increase in the revolving credit facility and the bank term notes at the Company’s request to an aggregate amount up to $850 million.
	On April 8, 2014, the Company entered into a $175 million term note maturing April 2024 bearing interest at a fixed rate of 4.533%. The interest rate on the term note increases to 6.283% if the Company is not rated by at least one rating agency or if the Company’s credit rating is downgraded. The proceeds from this term note were used to repay the $115 million outstanding on the Company’s line of credit at April 8, 2014, with the excess proceeds used for acquisitions.
	In 2011, the Company entered into a $100 million term note maturing August 5, 2021 bearing interest at a fixed rate of 5.54%. The interest rate on the term note increases to 7.29% if the notes are not rated by at least one rating agency, the credit rating on the notes is downgraded or if the Company’s credit rating is downgraded. The proceeds from this term note were used to fund acquisitions and investments in unconsolidated joint ventures.
	The Company also maintains a $150 million unsecured term note maturing April 13, 2016 bearing interest at 6.38%. The interest rate on the $150 million unsecured term note increases to 8.13% if the notes are not rated by at least one rating agency, the credit rating on the notes is downgraded or the Company’s credit rating is downgraded.
	The line of credit and term notes require the Company to meet certain financial covenants, measured on a quarterly basis, including prescribed leverage, fixed charge coverage, minimum net worth, limitations on additional indebtedness and limitations on dividend payouts. At March 31, 2015, the Company was in compliance with its debt covenants.
	We believe that if operating results remain consistent with historical levels and levels of other debt and liabilities remain consistent with amounts outstanding at March 31, 2015 the entire availability on the line of credit could be drawn without violating our debt covenants.
	The Company’s fixed rate term notes contain a provision that allows for the noteholders to call the debt upon a change of control of the Company at an amount that includes a make whole premium based on rates in effect on the date of the change of control.

Mortgages_Payable_and_Debt_Mat

Mortgages Payable and Debt Maturities	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Mortgages Payable and Debt Maturities	6	MORTGAGES PAYABLE AND DEBT MATURITIES
	Mortgages payable at March 31, 2015 and December 31, 2014 consist of the following:
	(dollars in thousands)		March 31,		December 31,
			2015		2014
	5.99% mortgage notes due May 1, 2026, secured by one self-storage facility with an aggregate net book value of $4.4 million, principal and interest paid monthly (effective interest rate 6.22%)			2,095		2,127
	Total mortgages payable		$	2,095	$	2,127
	The table below summarizes the Company’s debt obligations and interest rate derivatives at March 31, 2015. The estimated fair value of financial instruments is subjective in nature and is dependent on a number of important assumptions, including discount rates and relevant comparable market information associated with each financial instrument. The fair value of the fixed rate term notes and mortgage notes were estimated by discounting the future cash flows using the current rates at which similar loans would be made to borrowers with similar credit ratings and for the same remaining maturities. These assumptions are considered Level 2 inputs within the fair value hierarchy as described in Note 8. The carrying values of our variable rate debt instruments approximate their fair values as these debt instruments bear interest at current market rates that approximate market participant rates. This is considered a Level 2 input within the fair value hierarchy. The use of different market assumptions and estimation methodologies may have a material effect on the reported estimated fair value amounts. Accordingly, the estimates presented below are not necessarily indicative of the amounts the Company would realize in a current market exchange.
			Expected Maturity Date Including Discount
	(dollars in thousands)		2015		2016		2017		2018		2019		Thereafter		Total		Fair
																	Value
	Line of credit - variable rate LIBOR + 1.30% (1.48% at March 31, 2015)			—		—		—		—	$	63,000		—	$	63,000	$	63,000
	Notes Payable:
	Term note - fixed rate 6.38%			—	$	150,000		—		—		—		—	$	150,000	$	161,143
	Term note - variable rate LIBOR+1.40% (1.57% at March 31, 2015)			—		—		—		—		—	$	325,000	$	325,000	$	325,000
	Term note - fixed rate 5.54%			—		—		—		—		—	$	100,000	$	100,000	$	112,324
	Term note - fixed rate 4.533%			—		—		—		—		—	$	175,000	$	175,000	$	184,578
	Mortgage note - fixed rate 5.99%		$	102	$	142	$	151	$	160	$	170	$	1,370	$	2,095	$	2,266
	Interest rate derivatives - liability			—		—		—		—		—		—		—	$	17,318

Derivative_Financial_Instrumen

Derivative Financial Instruments

3 Months Ended

Mar. 31, 2015

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

7

DERIVATIVE FINANCIAL INSTRUMENTS

Interest rate swaps are used to adjust the proportion of total debt that is subject to variable interest rates. The interest rate swaps require the Company to pay an amount equal to a specific fixed rate of interest times a notional principal amount and to receive in return an amount equal to a variable rate of interest times the same notional amount. The notional amounts are not exchanged. No other cash payments are made unless the contract is terminated prior to its maturity, in which case the contract would likely be settled for an amount equal to its fair value. The Company enters into interest rate swaps with a number of major financial institutions to minimize counterparty credit risk.

The interest rate swaps qualify and are designated as hedges of the amount of future cash flows related to interest payments on variable rate debt. Therefore, the interest rate swaps are recorded in the consolidated balance sheet at fair value and the related gains or losses are deferred in shareholders’ equity as Accumulated Other Comprehensive Loss (“AOCL”). These deferred gains and losses are recognized in interest expense during the period or periods in which the related interest payments affect earnings. However, to the extent that the interest rate swaps are not perfectly effective in offsetting the change in value of the interest payments being hedged, the ineffective portion of these contracts is recognized in earnings immediately. Ineffectiveness was de minimis for the three months ended March 31, 2015, and 2014.

The Company has interest rate swap agreements in effect at March 31, 2015 as detailed below to effectively convert a total of $325 million of variable-rate debt to fixed-rate debt.

Notional Amount

Effective

Expiration

Fixed Rate

Floating

Date

Date

Paid

Rate Received

$125 Million

9/1/11

8/1/18

2.37

%

1 month LIBOR

$100 Million

12/30/11

12/29/17

1.6125

%

1 month LIBOR

$100 Million

9/4/13

9/4/18

1.371

%

1 month LIBOR

$100 Million

12/29/17

11/29/19

3.968

%

1 month LIBOR

$125 Million

8/1/18

6/1/20

4.193

%

1 month LIBOR

The interest rate swap agreements are the only derivative instruments, as defined by FASB ASC Topic 815 “Derivatives and Hedging”, held by the Company. During the three months ended March 31, 2015 and 2014, the net reclassification from AOCL to interest expense was $1.4 million and $1.4 million, respectively, based on payments made under the swap agreements. Based on current interest rates, the Company estimates that payments under the interest rate swaps will be approximately $5.5 million for the 12 months ended March 31, 2016. Payments made under the interest rate swap agreements will be reclassified to interest expense as settlements occur. The fair value of the swap agreements, including accrued interest, was a liability of $17.3 million and $13.3 million at March 31, 2015 and December 31, 2014, respectively.

The Company’s agreements with its interest rate swap counterparties contain provisions pursuant to which the Company could be declared in default of its derivative obligations if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender. The interest rate swap agreements also incorporate other loan covenants of the Company. Failure to comply with the loan covenant provisions would result in the Company being in default on the interest rate swap agreements. As of March 31, 2015, the Company had not posted any collateral related to the interest rate swap agreements. If the Company had breached any of these provisions as of March 31, 2015, it could have been required to settle its obligations under the agreements at their net termination value of $17.3 million.

The changes in AOCL for the three months ended March 31, 2015 and March 31, 2014 are summarized as follows:

(dollars in thousands)

Jan. 1, 2015

Jan. 1, 2014

to

to

Mar. 31, 2015

Mar. 31, 2014

Accumulated other comprehensive loss beginning of period

$

(13,005

)

$

(6,402

)

Realized loss reclassified from accumulated other comprehensive loss to interest expense

1,358

1,360

Unrealized loss from changes in the fair value of the effective portion of the interest rate swaps

(5,345

)

(3,289

)

Loss included in other comprehensive loss

(3,987

)

(1,929

)

Accumulated other comprehensive loss end of period

$

(16,992

)

$

(8,331

)

Fair_Value_Measurements

Fair Value Measurements

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value Measurements

8

FAIR VALUE MEASUREMENTS

The Company applies the provisions of ASC Topic 820 “Fair Value Measurements and Disclosures” in determining the fair value of its financial and nonfinancial assets and liabilities. ASC Topic 820 establishes a valuation hierarchy for disclosure of the inputs to valuation used to measure fair value. This hierarchy prioritizes the inputs into three broad levels as follows. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration. Level 3 inputs are unobservable inputs based on our own assumptions used to measure assets and liabilities at fair value. A financial asset or liability’s classification within the hierarchy is determined based on the lowest level input that is significant to the fair value measurement.

Refer to Note 6 for presentation of the fair values of debt obligations which are disclosed at fair value on a recurring basis.

The following table provides the assets and liabilities carried at fair value measured on a recurring basis as of March 31, 2015 and December 31, 2014 (in thousands):

Asset

Level 1

Level 2

Level 3

(Liability)

March 31, 2015

Interest rate swaps

(17,318

)

—

(17,318

)

—

December 31, 2014

Interest rate swaps

(13,341

)

—

(13,341

)

—

Interest rate swaps are over the counter securities with no quoted readily available Level 1 inputs, and therefore are measured at fair value using inputs that are directly observable in active markets and are classified within Level 2 of the valuation hierarchy, using the income approach.

During 2015, assets and liabilities measured at fair value on a non-recurring basis included the assets acquired and liabilities assumed in connection with the acquisition of six storage facilities (see note 4). To determine the fair value of land, the Company used prices per acre derived from observed transactions involving comparable land in similar locations, which is considered a Level 2 input. To determine the fair value of buildings, equipment and improvements, the Company used current replacement cost based on information derived from construction industry data by geographic region which is considered a Level 2 input. The replacement cost is then adjusted for the age, condition, and economic obsolescence associated with these assets, which are considered Level 3 inputs. The fair value of in-place customer leases is based on the rent lost due to the amount of time required to replace existing customers which is based on the Company’s historical experience with turnover at its facilities, which is a Level 3 input. Other assets acquired and liabilities assumed in the acquisitions consist primarily of prepaid or accrued real estate taxes and deferred revenues from advance monthly rentals paid by customers. The fair values of these assets and liabilities are based on their carrying values as they typically turn over within one year from the acquisition date and these are Level 3 inputs.

Investment_in_Joint_Ventures

Investment in Joint Ventures	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Investment in Joint Ventures	9	INVESTMENT IN JOINT VENTURES
	The Company has a 20% ownership interest in Sovran HHF Storage Holdings LLC (“Sovran HHF”), a joint venture that was formed in May 2008 to acquire self-storage properties that are managed by the Company. The carrying value of the Company’s investment at March 31, 2015 and December 31, 2014 was $45.2 million. 25 properties were acquired by Sovran HHF in 2008 for approximately $171.5 million and 14 additional properties were acquired by Sovran HHF in 2014 for $187.2 million. In 2008, the Company contributed $18.6 million to the joint venture as its share of capital required to fund the acquisitions. In 2012 the Company contributed an additional $1.2 million to the joint venture. In 2013 the Company received a return of capital distribution of $3.4 million as part of the refinancing of Sovran HHF. In 2014 the Company contributed an additional $28.6 million in cash to the joint venture as its share of capital required to fund acquisitions. As of March 31, 2015, the carrying value of the Company’s investment in Sovran HHF exceeds its share of the underlying equity in net assets of Sovran HHF by approximately $1.7 million as a result of the capitalization of certain acquisition related costs in 2008. This difference is included in the carrying value of the investment, which is assessed for other-than-temporary impairment on a periodic basis. No other-than-temporary impairments have been recorded on this investment.
	The Company has a 15% ownership interest in Sovran HHF Storage Holdings II LLC (“Sovran HHF II”), a joint venture that was formed in 2011 to acquire self-storage properties that are managed by the Company. The carrying value of the Company’s investment at March 31, 2015 and December 31, 2014 was $12.5 million and $12.6 million, respectively. 20 properties were acquired by Sovran HHF II during 2011 for approximately $166.1 million. During 2011, the Company contributed $12.8 million to the joint venture as its share of capital required to fund the acquisitions. Ten additional properties were acquired by Sovran HHF II during 2012 for approximately $29 million. During 2012, the Company contributed $2.4 million to the joint venture as its share of capital required to fund the acquisitions. The carrying value of this investment is assessed for other-than-temporary impairment on a periodic basis and no such impairments have been recorded on this investment.
	As manager of Sovran HHF and Sovran HHF II, the Company earns a management and call center fee of 7% of gross revenues which totaled $1.2 million and $0.9 million for the three months ended March 31, 2015 and 2014, respectively. The Company’s share of Sovran HHF and Sovran HHF II’s income for the three months ended March 31, 2015 and 2014 was $0.6 million and $0.4 million, respectively.
	The Company also has a 49% ownership interest in Iskalo Office Holdings, LLC, which owns the building that houses the Company’s headquarters and other tenants. The carrying value of the Company’s investment is a liability of $0.5 million at March 31, 2015 and December 31, 2014, and is included in accounts payable and accrued liabilities in the accompanying consolidated balance sheets. For the three months ended March 31, 2015, and 2014, the Company’s share of Iskalo Office Holdings, LLC’s income was $58,000 and $32,000, respectively. The Company paid rent to Iskalo Office Holdings, LLC of $0.3 million and $0.3 million during the three months ended March 31, 2015 and 2014, respectively.
	A summary of the unconsolidated joint ventures’ financial statements as of and for the three months ended March 31, 2015 is as follows:
	(dollars in thousands)		Sovran HHF			Sovran HHF			Iskalo Office
			Storage			Storage			Holdings, LLC
			Holdings LLC			Holdings II LLC
	Balance Sheet Data:
	Investment in storage facilities, net		$	340,176		$	184,204		$	—
	Investment in office building			—			—			4,956
	Other assets			5,758			4,210			3,423
	Total Assets		$	345,934		$	188,414		$	8,379
	Due to the Company		$	386		$	355		$	—
	Mortgages payable			124,520			102,696			9,177
	Other liabilities			3,710			2,259			360
	Total Liabilities			128,616			105,310			9,537
	Unaffiliated partners’ equity (deficiency)			173,854			70,644			(666	)
	Company equity (deficiency)			43,464			12,460			(492	)
	Total Partners’ Equity (Deficiency)			217,318			83,104			(1,158	)
	Total Liabilities and Partners’ Equity (Deficiency)		$	345,934		$	188,414		$	8,379
	Income Statement Data:
	Total revenues		$	9,435		$	7,170		$	397
	Property operating expenses			(3,216	)		(2,704	)		(144	)
	Administrative, management and call center fees			(700	)		(532	)		—
	Depreciation and amortization of customer list			(2,164	)		(1,048	)		(57	)
	Income tax expense			(53	)		(100	)		—
	Interest expense			(1,465	)		(1,313	)		(78	)
	Net income		$	1,837		$	1,473		$	118
	The Company does not guarantee the debt of Sovran HHF, Sovran HHF II, or Iskalo Office Holdings, LLC.
	We do not expect to have material future cash outlays relating to these joint ventures outside our share of capital for future acquisitions of properties.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	10	INCOME TAXES
	The Company qualifies as a REIT under the Internal Revenue Code of 1986, as amended, and will generally not be subject to corporate income taxes to the extent it distributes its taxable income to its shareholders and complies with certain other requirements.
	The Company has elected to treat one of its subsidiaries as a taxable REIT subsidiary. In general, the Company’s taxable REIT subsidiary may perform additional services for tenants and generally may engage in certain real estate or non-real estate related business. A taxable REIT subsidiary is subject to corporate federal and state income taxes. Deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities.
	For the three months ended March 31, 2015 and 2014, the Company recorded federal and state income tax expense of $0.4 million and $0.3 million, respectively. At March 31, 2015 and 2014, there were no material unrecognized tax benefits. Interest and penalties relating to uncertain tax positions will be recognized in income tax expense when incurred. As of March 31, 2015 and 2014, the Company had no interest or penalties related to uncertain tax positions. Net income taxes payable and the deferred tax liability of our taxable REIT subsidiary are classified within accounts payable and accrued liabilities in the consolidated balance sheet. As of March 31, 2015, the Company’s taxable REIT subsidiary has a current prepaid taxes of $0.3 million and a deferred tax liability of $1.3 million. The tax years 2011-2014 remain open to examination by the major taxing jurisdictions to which the Company is subject.

Earnings_Per_Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	11	EARNINGS PER SHARE
	The Company reports earnings per share data in accordance ASC Topic 260, “Earnings Per Share.” Effective January 1, 2009, FASB ASC Topic 260 was updated for the issuance of FASB Staff Position (“FSP”) EITF 03-6-1, “Determining Whether Instruments Granted in Share-Based Payment Transactions Are Participating Securities”, or FSP EITF 03-6-1, with transition guidance included in FASB ASC Topic 260-10-65-2. Under FSP EITF 03-6-1, unvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents, whether paid or unpaid, are participating securities and shall be included in the computation of earnings-per-share pursuant to the two-class method. The Company has calculated its basic and diluted earnings per share using the two-class method. The following table sets forth the computation of basic and diluted earnings per common share utilizing the two-class method.
	(in thousands except per share data)		Three Months		Three Months
			Ended		Ended
			Mar. 31, 2015		Mar. 31, 2014
	Numerator:
	Net income attributable to common shareholders		$	22,451	$	16,673
	Denominator:
	Denominator for basic earnings per share – weighted average shares			34,330		32,384
	Effect of Dilutive Securities:
	Stock options and non-vested stock			225		154
	Denominator for diluted earnings per share – adjusted weighted average shares and assumed conversion			34,555		32,538
	Basic earnings per common share attributable to common shareholders		$	0.65	$	0.51
	Diluted earnings per common share attributable to common shareholders		$	0.65	$	0.51
	Not included in the effect of dilutive securities above are 171,220 unvested restricted shares for the three months ended March 31, 2015, and 168,878 unvested restricted shares for the three months ended March 31, 2014, because their effect would be antidilutive.

Shareholders_Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Shareholders' Equity	12	SHAREHOLDERS’ EQUITY
	The following is a reconciliation of the changes in total shareholders’ equity for the period:
	(dollars in thousands)		Three Months
			Ended
			March 31, 2015
	Beginning balance of total shareholders’ equity		$	975,869
	Net proceeds from the issuance of common stock			122,129
	Exercise of stock options			502
	Earned portion of non-vested stock			1,612
	Stock option expense			36
	Adjustment to redemption value on noncontrolling redeemable Operating Partnership units			(1,228	)
	Net income attributable to common shareholders			22,451
	Change in fair value of derivatives			(3,987	)
	Dividends			(25,609	)
	Ending balance of total shareholders’ equity		$	1,091,775
	On March 3, 2015, the Company completed the public offering of 1,380,000 shares of its common stock at $90.40 per share. Net proceeds to the Company after deducting underwriting discounts and commissions and offering expenses were approximately $119.5 million. The Company used the net proceeds from the offering to repay a portion of the indebtedness outstanding on the Company’s unsecured line of credit.
	For the three months ended March 31, 2015, 9,500 shares of common stock were issued upon the exercise of stock options.
	On May 12, 2014, the Company entered into a continuous equity offering program (“Equity Program”) with Wells Fargo Securities, LLC (“Wells Fargo”), Jefferies LLC (“Jefferies”), SunTrust Robinson Humphrey, Inc. (“SunTrust”), Piper Jaffray & Co. (“Piper”), HSBC Securities (USA) Inc. (“HSBC”), and BB&T Capital Markets, a division of BB&T Securities, LLC (“BB&T”), pursuant to which the Company may sell from time to time up to $225 million in aggregate offering price of shares of the Company’s common stock. Actual sales under the Equity Program will depend on a variety of factors and conditions, including, but not limited to, market conditions, the trading price of the Company’s common stock, and determinations of the appropriate sources of funding for the Company. The Company expects to continue to offer, sell, and issue shares of common stock under the Equity Program from time to time based on various factors and conditions, although the Company is under no obligation to sell any shares under the Equity Program.
	During the three months ended March 31, 2015, the Company did not issue any shares of common stock under the Equity Program. As of March 31, 2015, the Company had $151.3 million available for issuance under the Equity Program.
	During the three months ended March 31, 2014, the Company issued 359,102 shares of common stock under a previous equity program at a weighted average issue price of $74.32 per share, generating net proceeds of $26.4 million after deducting $0.3 million of sales commissions payable to SunTrust.
	In 2013, the Company implemented a Dividend Reinvestment Plan. The Company issued 28,317 shares under the plan during the three months ended March 31, 2015.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2015
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	13	RECENT ACCOUNTING PRONOUNCEMENTS
	In April 2014, the FASB issued ASU 2014-08, “Presentation of Financial Statements (Topic 205) and Property, Plant and Equipment (Topic 360): Reporting Discontinued Operations and disclosures of Components of an Entity”. Under this ASU, only disposals representing a strategic shift in operations should be presented as discontinued operations. Those strategic shifts should have a major effect on the organization’s operations and financial results. The ASU also requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. It is effective for fiscal years, and interim periods within those years, beginning after December 15, 2014, with early adoption permitted. The Company adopted this guidance effective January 1, 2014 and the adoption is expected to significantly reduce the classification of property sales by the Company as discontinued operations.
	In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” which supersedes the revenue recognition requirements in “Revenue Recognition (Topic 605),” and requires an entity to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. ASU 2014-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. The Company has the option to apply the provisions of ASU 2014-09 either retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the new guidance recognized at the date of initial application. The Company has not yet completed its assessment of the impact that the adoption of ASU 2014-09 will have on its consolidated financial statements.
	In June 2014, the FASB issued ASU 2014-12, “Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period,” which requires a reporting entity to treat a performance target that affects vesting and that could be achieved after the requisite service period as a performance condition. ASU 2014-12 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2015. Early adoption is permitted. ASU 2014-12 may be adopted either prospectively for share-based payment awards granted or modified on or after the effective date, or retrospectively, using a modified retrospective approach. The modified retrospective approach would apply to share-based payment awards outstanding as of the beginning of the earliest annual period presented in the financial statements on adoption, and to all new or modified awards thereafter. The Company does not expect the adoption of ASU 2014-12 to have a material impact on its consolidated financial statements.
	In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis. This ASU is effective for annual reporting periods beginning after December 15, 2015 including interim periods within that reporting period. ASU 2015-02 amends the current consolidation model specifically as it relates to variable interest entities (“VIE’s”) and provides reporting entities with a revised consolidation analysis procedure. The Company is currently evaluating the impact that the adoption of this guidance will have on its financial position, results of operations, comprehensive income, cash flows and/or disclosures.
	In April 2015, the FASB issued ASU No. 2015-03, “Interest—Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs” (“ASU 2015-03”). ASU 2015-03 requires debt issuance costs to be presented in the balance sheet as a direct deduction from the carrying value of the associated debt liability, consistent with the presentation of a debt discount. Prior to the issuance of the standard, debt issuance costs were required to be presented in the balance sheet as an asset. The Company is currently assessing the impact that adopting this new accounting guidance will have on its consolidated financial statements and footnote disclosures. ASU 2015-03 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2015. Accordingly, the standard is effective for the Company on January 1, 2016.

Commitment_and_Contingencies

Commitment and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitment and Contingencies	14	COMMITMENT AND CONTINGENCIES
	At March 31, 2015, the Company was under contract to acquire nine self-storage facilities for cash consideration of approximately $72.4 million. Seven of the facilities were acquired in April and May of 2015 for $56.3 million. The Company has not yet determined the assignment of the purchase prices of these three facilities to the individual assets acquired. These acquisitions were funded with draws on the Company’s line of credit. The line of credit balance outstanding after the funding of the seven acquisitions was $138 million. The following is a summary of the second quarter 2015 acquisitions (dollars in thousands):
	State		Number of		Date of		Purchase
			Properties		Acquisition		Price
	Florida			1		4/1/15	$	6,300
	Texas			1		4/16/15		8,800
	Florida			1		4/21/15		8,750
	Florida			4		5/1/15		32,465
	Total acquired second quarter of 2015			7			$	56,315
	The purchase of the remaining facilities by the Company is subject to customary conditions to closing, and there is no assurance that these facilities will be acquired.
	On or about August 25, 2014, a putative class action was filed against the Company in the Superior Court of New Jersey Law Division Burlington County. The action seeks to obtain declaratory, injunctive and monetary relief for a class of consumers based upon alleged violations by the Company of the New Jersey Truth in Customer Contract, Warranty and Notice Act, the New Jersey Consumer Fraud Act and the New Jersey Insurance Producer Licensing Act. On October 17, 2014, the action was removed from the Superior Court of New Jersey Law Division Burlington County to the United States District Court for the District of New Jersey. The Company intends to vigorously defend the action, and the possibility of any adverse outcome cannot be determined at this time.

Reclassification

Reclassification	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Reclassification	15	RECLASSIFICATION
	Internet advertising expense, which had been included in the general and administrative expense line in prior year financial statements, has been reclassified to property operations and maintenance expense to conform with the current year presentation. The Company believes the classification of internet advertising expenses as property operations and maintenance expense is more consistent with industry trends. The amount of internet advertising expense that was reclassified for the three months ended March 31, 2014 was $1,420 (dollars in thousands).
	If such reclassification was in effect for the years ended December 31, 2014, 2013 and 2012, the consolidated statements of operations of the Company for such periods would show an increase in property operations and maintenance expense and a reduction of general and administrative expenses of (dollars in thousands) $5,570 for 2014, $4,803 for 2013, and $3,848 for 2012. There would be no effect on any other line items of the consolidated statements of operations. The consolidated statements of operations of the Company for such periods would have been presented as follows:
	CONSOLIDATED STATEMENTS OF OPERATIONS
			Year Ended December 31,
	(dollars in thousands, except per share data)		2014			2013			2012
	Revenues
	Rental income		$	302,044		$	253,384		$	217,906
	Other operating income			24,036			20,123			16,176
	Total operating revenues			326,080			273,507			234,082
	Expenses
	Property operations and maintenance			75,333			66,119			59,011
	Real estate taxes			32,097			26,496			22,076
	General and administrative			35,222			30,136			28,465
	Acquisition costs			7,359			3,129			4,328
	Operating leases of storage facilities			7,987			1,331			—
	Depreciation and amortization			51,749			45,233			40,542
	Total operating expenses			209,747			172,444			154,422
	Income from operations			116,333			101,063			79,660
	Other income (expenses)
	Interest expense			(34,578	)		(32,000	)		(33,166	)
	Interest income			40			40			4
	Gain on sale of storage facilities			5,176			—			—
	Gain on sale of real estate			—			421			687
	Equity in income of joint ventures			2,086			1,948			936
	Income from continuing operations			89,057			71,472			48,121
	Income from discontinued operations (including a gain on disposal of $2,431 in 2013 and $4,498 in 2012)			—			3,123			7,520
	Net income			89,057			74,595			55,641
	Net income attributable to noncontrolling interest			(526	)		(469	)		(513	)
	Net income attributable to common shareholders		$	88,531		$	74,126		$	55,128
	Earnings per common share attributable to common shareholders—basic
	Continuing operations		$	2.68		$	2.27		$	1.62
	Discontinued operations			—			0.1			0.26
	Earnings per share—basic		$	2.68		$	2.37		$	1.88
	Earnings per common share attributable to common shareholders—diluted
	Continuing operations		$	2.67		$	2.26		$	1.61
	Discontinued operations			—			0.1			0.26
	Earnings per share—diluted		$	2.67		$	2.36		$	1.87

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	16	SUBSEQUENT EVENTS
	On April 2, 2015, the Company declared a quarterly dividend of $0.75 per common share. The dividend was paid on April 27, 2015 to shareholders of record on April 17, 2015. The total dividend paid amounted to $26.6 million.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Changes and Error Corrections [Abstract]
Reclassification	Reclassification: Certain amounts from the 2014 financial statements have been reclassified to conform with the current year presentation. See Note 15.
Fair Value Measurements and Disclosures	The assets and liabilities of the other two acquired storage facilities, which primarily consist of tangible and intangible assets, are measured at fair value on the date of acquisition in accordance with the principles of FASB ASC Topic 820, “Fair Value Measurements and Disclosures.”
Discontinued Operations and Disclosures of Components of Entity	In April 2014, the FASB issued ASU 2014-08, “Presentation of Financial Statements (Topic 205) and Property, Plant and Equipment (Topic 360): Reporting Discontinued Operations and disclosures of Components of an Entity”. Under this ASU, only disposals representing a strategic shift in operations should be presented as discontinued operations. Those strategic shifts should have a major effect on the organization’s operations and financial results. The ASU also requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. It is effective for fiscal years, and interim periods within those years, beginning after December 15, 2014, with early adoption permitted. The Company adopted this guidance effective January 1, 2014 and the adoption is expected to significantly reduce the classification of property sales by the Company as discontinued operations.
Revenue from Contracts with Customers	In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” which supersedes the revenue recognition requirements in “Revenue Recognition (Topic 605),” and requires an entity to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. ASU 2014-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. The Company has the option to apply the provisions of ASU 2014-09 either retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initially applying the new guidance recognized at the date of initial application. The Company has not yet completed its assessment of the impact that the adoption of ASU 2014-09 will have on its consolidated financial statements.
Accounting for Share-Based Payments	In June 2014, the FASB issued ASU 2014-12, “Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period,” which requires a reporting entity to treat a performance target that affects vesting and that could be achieved after the requisite service period as a performance condition. ASU 2014-12 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2015. Early adoption is permitted. ASU 2014-12 may be adopted either prospectively for share-based payment awards granted or modified on or after the effective date, or retrospectively, using a modified retrospective approach. The modified retrospective approach would apply to share-based payment awards outstanding as of the beginning of the earliest annual period presented in the financial statements on adoption, and to all new or modified awards thereafter. The Company does not expect the adoption of ASU 2014-12 to have a material impact on its consolidated financial statements.
Consolidation Variable Interest Entity	In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis. This ASU is effective for annual reporting periods beginning after December 15, 2015 including interim periods within that reporting period. ASU 2015-02 amends the current consolidation model specifically as it relates to variable interest entities (“VIE’s”) and provides reporting entities with a revised consolidation analysis procedure. The Company is currently evaluating the impact that the adoption of this guidance will have on its financial position, results of operations, comprehensive income, cash flows and/or disclosures.
Presentation of Debt Issuance Costs	In April 2015, the FASB issued ASU No. 2015-03, “Interest—Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs” (“ASU 2015-03”). ASU 2015-03 requires debt issuance costs to be presented in the balance sheet as a direct deduction from the carrying value of the associated debt liability, consistent with the presentation of a debt discount. Prior to the issuance of the standard, debt issuance costs were required to be presented in the balance sheet as an asset. The Company is currently assessing the impact that adopting this new accounting guidance will have on its consolidated financial statements and footnote disclosures. ASU 2015-03 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2015. Accordingly, the standard is effective for the Company on January 1, 2016.

Organization_Tables

Organization (Tables)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Redeemable Noncontrolling Interest	Redemption value exceeded the value determined under the Company’s historical basis of accounting at those dates.
	(dollars in thousands)	Three Months
		Ended
		Mar. 31, 2015
	Beginning balance noncontrolling redeemable Operating Partnership Units	$	13,622
	Issuance of Operating Partnership Units		2,148
	Net income attributable to noncontrolling interests – consolidated joint venture		106
	Distributions		(117	)
	Adjustment to redemption value		1,228
	Ending balance noncontrolling redeemable Operating Partnership Units	$	16,987

Investment_in_Storage_Faciliti1

Investment in Storage Facilities (Tables)	3 Months Ended
	Mar. 31, 2015
Real Estate [Abstract]
Summary of Activity in Storage Facilities	The following summarizes our activity in storage facilities during the three months ended March 31, 2015.
	(dollars in thousands)
	Cost:
	Beginning balance	$	2,177,983
	Acquisition of storage facilities		134,043
	Improvements and equipment additions		5,242
	Net increase in construction in progress		157
	Dispositions		(828	)
	Ending balance	$	2,316,597
	Accumulated Depreciation:
	Beginning balance	$	411,701
	Depreciation expense during the period		13,172
	Dispositions		(109	)
	Ending balance	$	424,764
Schedule of Acquired Facilities and Purchase Price of Facilities	The purchase price of the six facilities has been assigned as follows:
	(dollars in thousands)									Consideration paid							Acquisition Date Fair Value
	State	Number of			Date of			Purchase		Cash Paid		Value of		Net Other			Land		Building,		In-Place		Closing
		Properties			Acquisition			Price				Operating		Liabilities					Equipment, and		Customer		Costs
												Partnership		(Assets)					Improvements		Leases		Expensed
												Units Issued		Assumed
	2015
	Connecticut		2			2/2/15		$	61,116	$	62,377	$	—	$	(1,261	)	$	19,389	$	41,727	$	—	$	—
	New York		2			2/2/15			57,900		59,103		—		(1,203	)		10,084		47,816		—		—
	Illinois		1			2/5/15			6,800		6,652		—		148			2,579		4,066		155		273
	Illinois		1			3/9/15			8,382		6,158		2,148		76			1,658		6,724		—		309
	Total acquired 2015		6					$	134,198	$	134,290	$	2,148	$	(2,240	)	$	33,710	$	100,333	$	155	$	582
Schedule of Fair Value of In-Place Customer Lease Intangible Assets	In-place customer leases are included in other assets on the Company’s balance sheet as follows:
	(Dollars in thousands)	Mar. 31,			Dec. 31,
		2015			2014
	In-place customer leases	$	19,927		$	19,867
	Accumulated amortization		(18,645	)		(17,663	)
	Net carrying value at the end of period	$	1,282		$	2,204
Summary of Revenues and Expenses Related to Sale of Properties Included in Company's Consolidated Statements of Operations	The following table summarizes the revenues and expenses up to the date of sale of the property sold in 2015 that are included in the Company’s consolidated statements of operations for 2015 and 2014.
	(Dollars in thousands)	Jan. 31, 2015			Jan. 31, 2014
		to			to
		Mar. 31, 2015			Mar. 31, 2014
	Total revenues	$	40		$	—
	Property operations and maintenance expense		(16	)		—
	Real estate tax expense		(5	)		—
	Depreciation and amortization expense		(9	)		—
	Loss on sale of storage facilities		(7	)		—
		$	3		$	—

Unsecured_Line_of_Credit_and_T1

Unsecured Line of Credit and Term Notes (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Borrowings Outstanding on Unsecured Line of Credit and Term Notes	Borrowings outstanding on our unsecured line of credit and term notes are as follows:
	(Dollars in thousands)	Mar. 31,		Dec. 31,
		2015		2014
	Revolving line of credit borrowings	$	63,000	$	49,000
	Term note due April 13, 2016		150,000		150,000
	Term note due June 4, 2020		325,000		325,000
	Term note due August 5, 2021		100,000		100,000
	Term note due April 8, 2024		175,000		175,000
	Total term notes payable	$	750,000	$	750,000

Mortgages_Payable_and_Debt_Mat1

Mortgages Payable and Debt Maturities (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Summary of Mortgage Payable	Mortgages payable at March 31, 2015 and December 31, 2014 consist of the following:
	(dollars in thousands)	March 31,		December 31,
		2015		2014
	5.99% mortgage notes due May 1, 2026, secured by one self-storage facility with an aggregate net book value of $4.4 million, principal and interest paid monthly (effective interest rate 6.22%)		2,095		2,127
	Total mortgages payable	$	2,095	$	2,127
Summary of Debt Obligation and Interest Rate Derivatives	Accordingly, the estimates presented below are not necessarily indicative of the amounts the Company would realize in a current market exchange.
		Expected Maturity Date Including Discount
	(dollars in thousands)	2015		2016		2017		2018		2019		Thereafter		Total		Fair
																Value
	Line of credit - variable rate LIBOR + 1.30% (1.48% at March 31, 2015)		—		—		—		—	$	63,000		—	$	63,000	$	63,000
	Notes Payable:
	Term note - fixed rate 6.38%		—	$	150,000		—		—		—		—	$	150,000	$	161,143
	Term note - variable rate LIBOR+1.40% (1.57% at March 31, 2015)		—		—		—		—		—	$	325,000	$	325,000	$	325,000
	Term note - fixed rate 5.54%		—		—		—		—		—	$	100,000	$	100,000	$	112,324
	Term note - fixed rate 4.533%		—		—		—		—		—	$	175,000	$	175,000	$	184,578
	Mortgage note - fixed rate 5.99%	$	102	$	142	$	151	$	160	$	170	$	1,370	$	2,095	$	2,266
	Interest rate derivatives - liability		—		—		—		—		—		—		—	$	17,318

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Swap Agreements	The Company has interest rate swap agreements in effect at March 31, 2015 as detailed below to effectively convert a total of $325 million of variable-rate debt to fixed-rate debt.
	Notional Amount	Effective			Expiration			Fixed Rate			Floating
		Date			Date			Paid			Rate Received
	$125 Million		9/1/11			8/1/18			2.37	%	1 month LIBOR
	$100 Million		12/30/11			12/29/17			1.6125	%	1 month LIBOR
	$100 Million		9/4/13			9/4/18			1.371	%	1 month LIBOR
	$100 Million		12/29/17			11/29/19			3.968	%	1 month LIBOR
	$125 Million		8/1/18			6/1/20			4.193	%	1 month LIBOR
Summary of Changes in AOCL	The changes in AOCL for the three months ended March 31, 2015 and March 31, 2014 are summarized as follows:
	(dollars in thousands)	Jan. 1, 2015			Jan. 1, 2014
		to			to
		Mar. 31, 2015			Mar. 31, 2014
	Accumulated other comprehensive loss beginning of period	$	(13,005	)	$	(6,402	)
	Realized loss reclassified from accumulated other comprehensive loss to interest expense		1,358			1,360
	Unrealized loss from changes in the fair value of the effective portion of the interest rate swaps		(5,345	)		(3,289	)
	Loss included in other comprehensive loss		(3,987	)		(1,929	)
	Accumulated other comprehensive loss end of period	$	(16,992	)	$	(8,331	)

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Assets and Liabilities Carried at Fair Value Measured on Recurring Basis	The following table provides the assets and liabilities carried at fair value measured on a recurring basis as of March 31, 2015 and December 31, 2014 (in thousands):
		Asset			Level 1		Level 2			Level 3
		(Liability)
	March 31, 2015
	Interest rate swaps		(17,318	)		—		(17,318	)		—
	December 31, 2014
	Interest rate swaps		(13,341	)		—		(13,341	)		—

Investment_in_Joint_Ventures_T

Investment in Joint Ventures (Tables)	3 Months Ended
	Mar. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Summary of Unconsolidated Joint Ventures' Financial Statements	A summary of the unconsolidated joint ventures’ financial statements as of and for the three months ended March 31, 2015 is as follows:
	(dollars in thousands)	Sovran HHF			Sovran HHF			Iskalo Office
		Storage			Storage			Holdings, LLC
		Holdings LLC			Holdings II LLC
	Balance Sheet Data:
	Investment in storage facilities, net	$	340,176		$	184,204		$	—
	Investment in office building		—			—			4,956
	Other assets		5,758			4,210			3,423
	Total Assets	$	345,934		$	188,414		$	8,379
	Due to the Company	$	386		$	355		$	—
	Mortgages payable		124,520			102,696			9,177
	Other liabilities		3,710			2,259			360
	Total Liabilities		128,616			105,310			9,537
	Unaffiliated partners’ equity (deficiency)		173,854			70,644			(666	)
	Company equity (deficiency)		43,464			12,460			(492	)
	Total Partners’ Equity (Deficiency)		217,318			83,104			(1,158	)
	Total Liabilities and Partners’ Equity (Deficiency)	$	345,934		$	188,414		$	8,379
	Income Statement Data:
	Total revenues	$	9,435		$	7,170		$	397
	Property operating expenses		(3,216	)		(2,704	)		(144	)
	Administrative, management and call center fees		(700	)		(532	)		—
	Depreciation and amortization of customer list		(2,164	)		(1,048	)		(57	)
	Income tax expense		(53	)		(100	)		—
	Interest expense		(1,465	)		(1,313	)		(78	)
	Net income	$	1,837		$	1,473		$	118

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Common Share	The following table sets forth the computation of basic and diluted earnings per common share utilizing the two-class method.
	(in thousands except per share data)	Three Months		Three Months
		Ended		Ended
		Mar. 31, 2015		Mar. 31, 2014
	Numerator:
	Net income attributable to common shareholders	$	22,451	$	16,673
	Denominator:
	Denominator for basic earnings per share – weighted average shares		34,330		32,384
	Effect of Dilutive Securities:
	Stock options and non-vested stock		225		154
	Denominator for diluted earnings per share – adjusted weighted average shares and assumed conversion		34,555		32,538
	Basic earnings per common share attributable to common shareholders	$	0.65	$	0.51
	Diluted earnings per common share attributable to common shareholders	$	0.65	$	0.51

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Reconciliation of Changes in Total Shareholders' Equity	The following is a reconciliation of the changes in total shareholders’ equity for the period:
	(dollars in thousands)	Three Months
		Ended
		March 31, 2015
	Beginning balance of total shareholders’ equity	$	975,869
	Net proceeds from the issuance of common stock		122,129
	Exercise of stock options		502
	Earned portion of non-vested stock		1,612
	Stock option expense		36
	Adjustment to redemption value on noncontrolling redeemable Operating Partnership units		(1,228	)
	Net income attributable to common shareholders		22,451
	Change in fair value of derivatives		(3,987	)
	Dividends		(25,609	)
	Ending balance of total shareholders’ equity	$	1,091,775

Commitment_and_Contingencies_T

Commitment and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Summary of Self Storage Facilities Acquisitions	The following is a summary of the second quarter 2015 acquisitions (dollars in thousands):
	State	Number of		Date of		Purchase
		Properties		Acquisition		Price
	Florida		1		4/1/15	$	6,300
	Texas		1		4/16/15		8,800
	Florida		1		4/21/15		8,750
	Florida		4		5/1/15		32,465
	Total acquired second quarter of 2015		7			$	56,315

Reclassification_Tables

Reclassification (Tables)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Schedule of Consolidated Statements of Operations	The consolidated statements of operations of the Company for such periods would have been presented as follows:
	CONSOLIDATED STATEMENTS OF OPERATIONS
		Year Ended December 31,
	(dollars in thousands, except per share data)	2014			2013			2012
	Revenues
	Rental income	$	302,044		$	253,384		$	217,906
	Other operating income		24,036			20,123			16,176
	Total operating revenues		326,080			273,507			234,082
	Expenses
	Property operations and maintenance		75,333			66,119			59,011
	Real estate taxes		32,097			26,496			22,076
	General and administrative		35,222			30,136			28,465
	Acquisition costs		7,359			3,129			4,328
	Operating leases of storage facilities		7,987			1,331			—
	Depreciation and amortization		51,749			45,233			40,542
	Total operating expenses		209,747			172,444			154,422
	Income from operations		116,333			101,063			79,660
	Other income (expenses)
	Interest expense		(34,578	)		(32,000	)		(33,166	)
	Interest income		40			40			4
	Gain on sale of storage facilities		5,176			—			—
	Gain on sale of real estate		—			421			687
	Equity in income of joint ventures		2,086			1,948			936
	Income from continuing operations		89,057			71,472			48,121
	Income from discontinued operations (including a gain on disposal of $2,431 in 2013 and $4,498 in 2012)		—			3,123			7,520
	Net income		89,057			74,595			55,641
	Net income attributable to noncontrolling interest		(526	)		(469	)		(513	)
	Net income attributable to common shareholders	$	88,531		$	74,126		$	55,128
	Earnings per common share attributable to common shareholders—basic
	Continuing operations	$	2.68		$	2.27		$	1.62
	Discontinued operations		—			0.1			0.26
	Earnings per share—basic	$	2.68		$	2.37		$	1.88
	Earnings per common share attributable to common shareholders—diluted
	Continuing operations	$	2.67		$	2.26		$	1.61
	Discontinued operations		—			0.1			0.26
	Earnings per share—diluted	$	2.67		$	2.36		$	1.87

Organization_Additional_Inform

Organization - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2008	Dec. 31, 2012	Dec. 31, 2011
	Facility		Property	Property	Property
	Property
	States
Organization [Line Items]
Number of self-storage properties owned and managed	521
Number of states in which self-storage properties owned and managed	25
Number of properties managed with no ownership	19
Percentage of ownership interest of the subsidiary and its limited partnership which controls the operations of the Operating Partnership	99.50%
Units of redeemable noncontrolling interest in operating partnership	178,866	155,484
Noncontrolling limited partnership unit redemption value	One common share or cash
Number of units issued for acquisition	23,382
Fair value of units, issued for acquisition	$2.10
Number of self storage properties acquired	1
Sovran HHF Storage Holdings LLC [Member] | Equity Method Investee [Member]
Organization [Line Items]
Number of properties owned and managed under twenty-percent stake joint venture	39		25
Percentage ownership in unconsolidated joint venture	20.00%
Sovran HHF Storage Holdings II LLC [Member] | Equity Method Investee [Member]
Organization [Line Items]
Percentage ownership in unconsolidated joint venture	15.00%
Number of properties owned and managed under fifteen-percent stake joint venture	30			10	20
Geographic Concentration Risk [Member] | Texas and Florida [Member] | Revenue [Member]
Organization [Line Items]
Concentration risk, percentage	40.00%
Geographic Concentration Risk [Member] | Houston Texas [Member] | Revenue [Member]
Organization [Line Items]
Concentration risk, percentage	12.00%

Organization_Summary_of_Redeem

Organization - Summary of Redeemable Noncontrolling Interest (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Redeemable Noncontrolling Interest, Equity, Fair Value [Abstract]
Beginning balance noncontrolling redeemable Operating Partnership Units	$13,622
Issuance of Operating Partnership Units	2,148
Net income attributable to noncontrolling interests - consolidated joint venture	106	102	526	469	513
Distributions	-117	-135
Adjustment to redemption value	1,228
Ending balance noncontrolling redeemable Operating Partnership Units	$16,987		$13,622

Stock_Based_Compensation_Addit

Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock option expense	$36,000	$36,000
Amortization of non-vested stock grants	$1,612,000	$1,193,000
Stock options exercised by employees and directors	9,500	1,500
Number of shares of non-vested stock that vested	5,234	9,880

Investment_in_Storage_Faciliti2

Investment in Storage Facilities - Summary of Activity in Storage Facilities (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Cost:
Beginning balance	$2,177,983
Acquisition of storage facilities	134,043
Improvements and equipment additions	5,242
Net increase in construction in progress	157
Dispositions	-828
Ending balance	2,316,597
Accumulated Depreciation:
Beginning balance	411,701
Depreciation expense during the period	13,172
Dispositions	-109
Ending balance	$424,764

Investment_in_Storage_Faciliti3

Investment in Storage Facilities - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Feb. 02, 2015
	Property			Facility
	Facility
Investment Holdings [Line Items]
Number of facilities acquired	6
Cash paid for properties acquired	$134,300,000
Deposits paid at the time of contract		250,000,000
Amortization period for in-place customer leases on a straight-line basis	12 months
Issuance of Operating Partnership Units	2,100,000
Net other liabilities (assets) assumed	200,000
Settlement of a straight-line rent liability	2,400,000
Amortization expense related to in-place customer leases	1,000,000	700,000
Amortization expense expected for 2015	2,300,000
Amortization expense expected for 2016	13,000
Number of properties sold	1
Carrying value of properties sold	698,000
Net proceeds from the sale of storage facility	711,000
Loss on sale of storage facility	-7,000		5,176,000
One Property [Member]
Investment Holdings [Line Items]
Net proceeds from the sale of storage facility	$691,000
Connecticut and New York [Member]
Investment Holdings [Line Items]
Number of facilities acquired and leased since November 1, 2013				4
Illinois [Member]
Investment Holdings [Line Items]
Number of facilities acquired included in operations	2

Investment_in_Storage_Faciliti4

Investment in Storage Facilities - Schedule of Acquired Facilities and Purchase Price of Facilities (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Facility
Investment Holdings [Line Items]
Number of Properties	6
Cash Paid	$134,300
Closing Costs Expensed	582	2,778	7,359	3,129	4,328
Acquisitions 2015 [Member]
Investment Holdings [Line Items]
Number of Properties	6
Purchase Price	134,198
Cash Paid	134,290
Consideration paid Value of Operating Partnership Units Issued	2,148
Net Other Liabilities (Assets) Assumed	-2,240
Land	33,710
Acquisition Date Building, Equipment, and Improvements	100,333
Fair Value In-Place Customers Leases	155
Closing Costs Expensed	582
Connecticut [Member] | Date of Acquisition, 2/2/2015 [Member]
Investment Holdings [Line Items]
Number of Properties	2
Date of Acquisition	2-Feb-15
Purchase Price	61,116
Cash Paid	62,377
Net Other Liabilities (Assets) Assumed	-1,261
Land	19,389
Acquisition Date Building, Equipment, and Improvements	41,727
New York [Member] | Date of Acquisition, 2/2/2015 [Member]
Investment Holdings [Line Items]
Number of Properties	2
Date of Acquisition	2-Feb-15
Purchase Price	57,900
Cash Paid	59,103
Net Other Liabilities (Assets) Assumed	-1,203
Land	10,084
Acquisition Date Building, Equipment, and Improvements	47,816
Illinois [Member] | Date of Acquisition, 2/5/2015 [Member]
Investment Holdings [Line Items]
Number of Properties	1
Date of Acquisition	5-Feb-15
Purchase Price	6,800
Cash Paid	6,652
Net Other Liabilities (Assets) Assumed	148
Land	2,579
Acquisition Date Building, Equipment, and Improvements	4,066
Fair Value In-Place Customers Leases	155
Closing Costs Expensed	273
Illinois [Member] | Date of Acquisition, 3/9/2015 [Member]
Investment Holdings [Line Items]
Number of Properties	1
Date of Acquisition	9-Mar-15
Purchase Price	8,382
Cash Paid	6,158
Consideration paid Value of Operating Partnership Units Issued	2,148
Net Other Liabilities (Assets) Assumed	76
Land	1,658
Acquisition Date Building, Equipment, and Improvements	6,724
Closing Costs Expensed	$309

Investment_in_Storage_Faciliti5

Investment in Storage Facilities - Schedule of Fair Value of In-Place Customer Lease Intangible Assets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Real Estate [Abstract]
In-place customer leases	$19,927	$19,867
Accumulated amortization	-18,645	-17,663
Net carrying value at the end of period	$1,282	$2,204

Investment_in_Storage_Faciliti6

Investment in Storage Facilities - Summary of Revenues and Expenses Related to Sale of Properties Included in Company's Consolidated Statements of Operations (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues	$85,408	$75,457	$326,080	$273,507	$234,082
Property operations and maintenance expense	-20,559	-18,484	-75,333	-66,119	-59,011
Real estate tax expense	-8,920	-8,066	-32,097	-26,496	-22,076
Depreciation and amortization expense	-14,181	-11,942	-51,749	-45,233	-40,542
Loss on sale of storage facilities	-7		5,176
Properties Sold In Two Thousand And Fifteen Member
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues	40
Property operations and maintenance expense	-16
Real estate tax expense	-5
Depreciation and amortization expense	-9
Loss on sale of storage facilities	-7
Total income from discontinued operations	$3

Unsecured_Line_of_Credit_and_T2

Unsecured Line of Credit and Term Notes - Borrowings Outstanding on Unsecured Line of Credit and Term Notes (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Unsecured Line Of Credit And Term Notes [Line Items]
Revolving line of credit borrowings	$63,000	$49,000
Total term notes payable	750,000	750,000
Term Note Due April 13, 2016 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Total term notes payable	150,000	150,000
Term Note Due June 4, 2020 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Total term notes payable	325,000	325,000
Term Note Due August 5, 2021 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Total term notes payable	100,000	100,000
Term Note Due April 8, 2024 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Total term notes payable	$175,000	$175,000

Unsecured_Line_of_Credit_and_T3

Unsecured Line of Credit and Term Notes - Additional Information (Detail) (USD $)	3 Months Ended	0 Months Ended	12 Months Ended
	Mar. 31, 2015	Apr. 08, 2014	Dec. 31, 2011	Dec. 31, 2014	Dec. 10, 2014
Unsecured Line Of Credit And Term Notes [Line Items]
Unsecured term note	$750,000,000			$750,000,000
Revolving credit limit	300,000,000				175,000,000
Maturity on June 4, 2020 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Unsecured term note	325,000,000
Basis spread over LIBOR	1.40%
Maturity on December 10, 2019 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Basis spread over LIBOR	1.30%
Facility fee	0.20%
Interest rate, line of credit facility	1.48%			1.46%
Amount available on unsecured line of credit	237,000,000
Line of credit facility, expiration date	10-Dec-19
Maturity on December 10, 2019 [Member] | Amended Agreement [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Increase in the revolving credit facility	850,000,000
Maturity in April, 2024 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Line of credit facility, expiration date	8-Apr-24
Additional secured term note		175,000,000
Term note stated interest rate	4.53%
Increase in interest rate on term loan	6.28%
Repayment of Lines of Credit		115,000,000
Maturity in August 2021 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Line of credit facility, expiration date	5-Aug-21
Additional secured term note			100,000,000
Term note stated interest rate			5.54%
Increase in interest rate on term loan			7.29%
Maturity in April 2016 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Unsecured term note	$150,000,000
Line of credit facility, expiration date	13-Apr-16
Term note stated interest rate	6.38%
Increase in interest rate on term loan	8.13%

Mortgages_Payable_and_Debt_Mat2

Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Mortgages payable	$2,095	$2,127
5.99% Mortgage Notes Due May 1, 2026 [Member]
Debt Instrument [Line Items]
Mortgages payable	$2,095	$2,127

Mortgages_Payable_and_Debt_Mat3

Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Parenthetical) (Detail) (5.99% Mortgage Notes Due May 1, 2026 [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
	Facility
5.99% Mortgage Notes Due May 1, 2026 [Member]
Debt Instrument [Line Items]
Term note stated interest rate	5.99%
Mortgage note due date	1-May-26
Self-storage facilities	1
Aggregate net book value of property pledged for mortgage note	$4.40
Effective interest rate	6.22%

Mortgages_Payable_and_Debt_Mat4

Mortgages Payable and Debt Maturities - Summary of Debt Obligation and Interest Rate Derivatives (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Line of credit	$63,000	$49,000
Term notes	750,000	750,000
Mortgage note, total	2,095	2,127
Interest rate derivatives - liability	17,318	13,341
Line of credit - variable rate LIBOR + 1.30% (1.48% at March 31, 2015) [Member]
Debt Instrument [Line Items]
Payable due 2019	63,000
Line of credit	63,000
Debt instrument, fair value	63,000
Term Note - Fixed Rate 6.38% [Member]
Debt Instrument [Line Items]
Payables due 2016	150,000
Term notes	150,000
Term note, fair value	161,143
Term note - variable rate LIBOR+1.40% (1.57% at March 31, 2015) [Member]
Debt Instrument [Line Items]
Payables due Thereafter	325,000
Term notes	325,000
Term note, fair value	325,000
Term Note - Fixed Rate 5.54% [Member]
Debt Instrument [Line Items]
Payables due Thereafter	100,000
Term notes	100,000
Term note, fair value	112,324
Term Note - Fixed Rate 4.533% [Member]
Debt Instrument [Line Items]
Payables due Thereafter	175,000
Term notes	175,000
Term note, fair value	184,578
Mortgage Note - Fixed Rate 5.99% [Member]
Debt Instrument [Line Items]
Payable due 2015	102
Payables due 2016	142
Payables due 2017	151
Payable due 2018	160
Payable due 2019	170
Payables due Thereafter	1,370
Mortgage note, total	2,095
Debt instrument, fair value	$2,266

Mortgages_Payable_and_Debt_Mat5

Mortgages Payable and Debt Maturities - Summary of Debt Obligation and Interest Rate Derivatives (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2015
Line of credit - variable rate LIBOR + 1.30% (1.48% at March 31, 2015) [Member]
Debt Instrument [Line Items]
Interest rate at end of period	1.48%
Basis spread over LIBOR	1.30%
Term Note - Fixed Rate 6.38% [Member]
Debt Instrument [Line Items]
Interest rate at end of period	6.38%
Term note - variable rate LIBOR+1.40% (1.57% at March 31, 2015) [Member]
Debt Instrument [Line Items]
Interest rate at end of period	1.57%
Basis spread over LIBOR	1.40%
Term Note - Fixed Rate 5.54% [Member]
Debt Instrument [Line Items]
Interest rate at end of period	5.54%
Term Note - Fixed Rate 4.533% [Member]
Debt Instrument [Line Items]
Interest rate at end of period	4.53%
Mortgage Note - Fixed Rate 5.99% [Member]
Debt Instrument [Line Items]
Interest rate at end of period	5.99%

Derivative_Financial_Instrumen2

Derivative Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2016	Dec. 31, 2014
Derivative [Line Items]
Interest Expense	($1,358,000)	($1,360,000)
Fair value of interest rate swap agreements	17,318,000			13,341,000
Net termination value	17,300,000
Interest Expense [Member]
Derivative [Line Items]
Interest Expense	1,400,000	1,400,000
Scenario, Forecast [Member]
Derivative [Line Items]
Estimated payments to be made under interest rate swaps			5,500,000
Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount of variable rate debt swapped	$325,000,000

Derivative_Financial_Instrumen3

Derivative Financial Instruments - Summary of Interest Rate Swap Agreements (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	$125,000,000
Effective Date	1-Sep-11
Expiration Date	1-Aug-18
Fixed Rate Paid	2.37%
Interest Rate Swap [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Floating Rate Received	1 month LIBOR
Interest Rate Swap One [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Effective Date	30-Dec-11
Expiration Date	29-Dec-17
Fixed Rate Paid	1.61%
Interest Rate Swap One [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Floating Rate Received	1 month LIBOR
Interest Rate Swap Two [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Effective Date	4-Sep-13
Expiration Date	4-Sep-18
Fixed Rate Paid	1.37%
Interest Rate Swap Two [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Floating Rate Received	1 month LIBOR
Interest Rate Swap Three [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Effective Date	29-Dec-17
Expiration Date	29-Nov-19
Fixed Rate Paid	3.97%
Interest Rate Swap Three [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Floating Rate Received	1 month LIBOR
Interest Rate Swap Four [Member]
Derivative [Line Items]
Notional Amount	$125,000,000
Effective Date	1-Aug-18
Expiration Date	1-Jun-20
Fixed Rate Paid	4.19%
Interest Rate Swap Four [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Floating Rate Received	1 month LIBOR

Derivative_Financial_Instrumen4

Derivative Financial Instruments - Summary of Changes in AOCL (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Accumulated other comprehensive loss beginning of period	($13,005)	($6,402)
Realized loss reclassified from accumulated other comprehensive loss to interest expense	1,358	1,360
Unrealized loss from changes in the fair value of the effective portion of the interest rate swaps	-5,345	-3,289
Loss included in other comprehensive loss	-3,987	-1,929
Accumulated other comprehensive loss end of period	($16,992)	($8,331)

Fair_Value_Measurements_Assets

Fair Value Measurements - Assets and Liabilities Carried at Fair Value Measured on Recurring Basis (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Interest rate swaps	($17,318)	($13,341)
Interest Rate Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Interest rate swaps	-17,318	-13,341
Interest Rate Swap [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Interest rate swaps	($17,318)	($13,341)

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015
	Facility
Fair Value Disclosures [Abstract]
Number of storage facilities acquired	6

Investment_in_Joint_Ventures_A

Investment in Joint Ventures - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2008
						Property	Property
Schedule of Equity Method Investments [Line Items]
Investment at carrying value	$1,091,775,000		$975,869,000
Company's share in income (loss) of joint venture	646,000	458,000	2,086,000	1,948,000	936,000
Iskalo Office Holdings, LLC [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	49.00%
Investment at carrying value	-492,000		-500,000
Company's share in income (loss) of joint venture	58,000	32,000
Rent paid during the period	300,000	300,000
Sovran HHF Storage Holdings II LLC [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	15.00%
Payment for property acquisition					29,000,000	166,100,000
Contribution of company to joint venture as share in capital					2,400,000	12,800,000
Investment at carrying value	12,460,000		12,600,000
Number of properties owned and managed under fifteen-percent stake joint venture	30				10	20
Sovran HHF and Sovran HHF II [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Management and call center fee as a percentage of revenues	7.00%
Management and call center fee earned	1,200,000	900,000
Company's share in income (loss) of joint venture	600,000	400,000
Sovran HHF Storage Holdings LLC [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	20.00%
Investment at carrying value	45,200,000		45,200,000
Payment for property acquisition			187,200,000				171,500,000
Number of properties owned and managed under twenty-percent stake joint venture	39						25
Additional number of properties owned and managed under twenty-percent stake joint venture			14
Contribution of company to joint venture as share in capital			28,600,000		1,200,000		18,600,000
Receipt of return of capital distribution				3,400,000
Excess of investment over net asset due to capitalization of acquisition related costs	1,700,000
Other-than-temporary impairment recorded on investment	0
Investment at carrying value	$43,464,000

Investment_in_Joint_Ventures_S

Investment in Joint Ventures - Summary of Unconsolidated Joint Ventures' Financial Statements (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Investment in storage facilities, net	$1,891,833		$1,766,282
Other assets	8,925		9,298
Total Assets	1,982,178		1,854,800
Mortgages payable	2,095		2,127
Total Liabilities	873,416		865,309
Company equity (deficiency)	1,091,775		975,869
Depreciation and amortization of customer list	-14,181	-11,942	-51,749	-45,233	-40,542
Income tax expense	-400	-300
Interest expense	-9,161	-7,343	-34,578	-32,000	-33,166
Sovran HHF Storage Holdings LLC [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investment in storage facilities, net	340,176
Other assets	5,758
Total Assets	345,934
Due to the Company	386
Mortgages payable	124,520
Other liabilities	3,710
Total Liabilities	128,616
Unaffiliated partners' equity (deficiency)	173,854
Company equity (deficiency)	43,464
Total Partners' Equity (Deficiency)	217,318
Total Liabilities and Partners' Equity (Deficiency)	345,934
Total revenues	9,435
Property operating expenses	-3,216
Administrative, management and call center fees	-700
Depreciation and amortization of customer list	-2,164
Income tax expense	-53
Interest expense	-1,465
Net income	1,837
Sovran HHF Storage Holdings II LLC [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investment in storage facilities, net	184,204
Other assets	4,210
Total Assets	188,414
Due to the Company	355
Mortgages payable	102,696
Other liabilities	2,259
Total Liabilities	105,310
Unaffiliated partners' equity (deficiency)	70,644
Company equity (deficiency)	12,460		12,600
Total Partners' Equity (Deficiency)	83,104
Total Liabilities and Partners' Equity (Deficiency)	188,414
Total revenues	7,170
Property operating expenses	-2,704
Administrative, management and call center fees	-532
Depreciation and amortization of customer list	-1,048
Income tax expense	-100
Interest expense	-1,313
Net income	1,473
Iskalo Office Holdings, LLC [Member] | Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investment in office building	4,956
Other assets	3,423
Total Assets	8,379
Mortgages payable	9,177
Other liabilities	360
Total Liabilities	9,537
Unaffiliated partners' equity (deficiency)	-666
Company equity (deficiency)	-492		-500
Total Partners' Equity (Deficiency)	-1,158
Total Liabilities and Partners' Equity (Deficiency)	8,379
Total revenues	397
Property operating expenses	-144
Depreciation and amortization of customer list	-57
Interest expense	-78
Net income	$118

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Federal and state income tax expense	$400,000	$300,000
Unrecognized tax benefits	0	0
Interest or penalties related to uncertain tax positions	0	0
Current prepaid taxes	300,000
Deferred tax liability	$1,300,000
Tax years open to examination	2011-2014

Earnings_Per_Share_Computation

Earnings Per Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income attributable to common shareholders	$22,451	$16,673	$88,531	$74,126	$55,128
Denominator:
Denominator for basic earnings per share - weighted average shares	34,329,768	32,383,996
Effect of Dilutive Securities:
Stock options and non-vested stock	225,000	154,000
Denominator for diluted earnings per share - adjusted weighted average shares and assumed conversion	34,554,871	32,538,429
Basic earnings per common share attributable to common shareholders	$0.65	$0.51	$2.68	$2.37	$1.88
Diluted earnings per common share attributable to common shareholders	$0.65	$0.51	$2.67	$2.36	$1.87

Earnings_Per_Share_Additional_

Earnings Per Share - Additional Information (Detail) (Restricted Stock [Member])	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities not included in the effect of dilutive securities	171,220	168,878

Shareholders_Equity_Reconcilia

Shareholders' Equity - Reconciliation of Changes in Total Shareholders' Equity (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Beginning balance	$975,869,000
Net proceeds from the issuance of common stock	122,129,000
Exercise of stock options	502,000
Earned portion of non-vested stock	1,612,000	1,193,000
Stock option expense	36,000	36,000
Adjustment to redemption value on noncontrolling redeemable Operating Partnership units	-1,228,000
Net income attributable to common shareholders	22,451,000	16,673,000	88,531,000	74,126,000	55,128,000
Change in fair value of derivatives	-3,987,000	-1,929,000
Dividends	-25,609,000
Ending balance	$1,091,775,000		$975,869,000

Shareholders_Equity_Additional

Shareholders' Equity - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended
	Mar. 03, 2015	Mar. 31, 2015	Mar. 31, 2014	Mar. 03, 2015	12-May-14
Stockholders Equity [Line Items]
Common stock shares issued under equity offering program	1,380,000
Common stock, price per share, public offering	$90.40			$90.40
Proceeds from issuance of common stock	$119,500,000
Common stock issued upon exercise of stock options		9,500	1,500
Common stock value authorized under equity offering program					225,000,000
Shares issued under dividend reinvestment plan		28,317
Equity Program [Member]
Stockholders Equity [Line Items]
Common stock shares issued under equity offering program		0	359,102
Proceeds from issuance of common stock			26,400,000
Common stock, value reserved for future issuance		151,300,000
Weighted average issue price of common stock			74.32
SunTrust [Member] | Equity Program [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions			300,000

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014	31-May-15	4-May-15	Apr. 30, 2015
In Thousands, unless otherwise specified	Facility		Facility		Facility
Commitment And Contingencies [Line Items]
Payment for self-storage facilities under contract	$72,400
Number of self-storage facilities under contract to be purchased	9
Line of credit balance outstanding after funding of seven acquisitions	63,000	49,000
Acquisition 2015 [Member] | Subsequent Event [Member]
Commitment And Contingencies [Line Items]
Payment for self-storage facilities under contract					56,300
Number of self-storage facilities under contract to be purchased			7		7
Line of credit balance outstanding after funding of seven acquisitions				$138,000

Commitments_and_Contingencies_1

Commitments and Contingencies - Summary of Self Storage Facilities Acquisitions (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2015	Mar. 31, 2015
	Facility	Facility
Significant Acquisitions and Disposals [Line Items]
Number of Properties		9
Purchase Price		$72,400
Scenario, Forecast [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Properties	7
Purchase Price	56,315
Date of Acquisition 4/1/2015 [Member] | Florida [Member] | Scenario, Forecast [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Properties	1
Date of Acquisition	1-Apr-15
Purchase Price	6,300
Date of Acquisition 4/16/2015 [Member] | Texas [Member] | Scenario, Forecast [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Properties	1
Date of Acquisition	16-Apr-15
Purchase Price	8,800
Date of Acquisition 4/21/2015 [Member] | Florida [Member] | Scenario, Forecast [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Properties	1
Date of Acquisition	21-Apr-15
Purchase Price	8,750
Date of Acquisition 5/1/2015 [Member] | Florida [Member] | Scenario, Forecast [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Properties	4
Date of Acquisition	1-May-15
Purchase Price	$32,465

Reclassification_Additional_In

Reclassification - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
General and administrative expenses	$9,406	$8,536	$35,222	$30,136	$28,465
Restatement Adjustment [Member]
Avertising Expense		1,420
General and administrative expenses			($5,570)	($4,803)	($3,848)

Reclassification_Schedule_of_C

Reclassification - Schedule of Consolidated Statements of Operations (Detail) (USD $)	3 Months Ended		12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Rental income	$78,886	$69,953	$302,044	$253,384	$217,906
Other operating income	6,522	5,504	24,036	20,123	16,176
Total operating revenues	85,408	75,457	326,080	273,507	234,082
Expenses
Property operations and maintenance	20,559	18,484	75,333	66,119	59,011
Real estate taxes	8,920	8,066	32,097	26,496	22,076
General and administrative	9,406	8,536	35,222	30,136	28,465
Acquisition costs	582	2,778	7,359	3,129	4,328
Operating leases of storage facilities	683	1,997	7,987	1,331
Depreciation and amortization	14,181	11,942	51,749	45,233	40,542
Total operating expenses	54,331	51,803	209,747	172,444	154,422
Income from operations	31,077	23,654	116,333	101,063	79,660
Other income (expenses)
Interest expense	-9,161	-7,343	-34,578	-32,000	-33,166
Interest income	2	6	40	40	4
Gain on sale of storage facilities	-7		5,176
Gain on sale of real estate				421	687
Equity in income of joint ventures	646	458	2,086	1,948	936
Income from continuing operations			89,057	71,472	48,121
Income from discontinued operations (including a gain on disposal of $2,431 in 2013 and $4,498 in 2012)				3,123	7,520
Net income	22,557	16,775	89,057	74,595	55,641
Net income attributable to noncontrolling interest	-106	-102	-526	-469	-513
Net income attributable to common shareholders	$22,451	$16,673	$88,531	$74,126	$55,128
Earnings per common share attributable to common shareholders - basic
Continuing operations			$2.68	$2.27	$1.62
Discontinued operations				$0.10	$0.26
Earnings per share - basic	$0.65	$0.51	$2.68	$2.37	$1.88
Earnings per common share attributable to common shareholders - diluted
Continuing operations			$2.67	$2.26	$1.61
Discontinued operations				$0.10	$0.26
Earnings per share - diluted	$0.65	$0.51	$2.67	$2.36	$1.87

Reclassification_Schedule_of_C1

Reclassification - Schedule of Consolidated Statements of Operations (Parenthetical) (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Variable Interests And Equity Method Investments Disclosure [Abstract]
Gain on disposal from discontinued operations	$2,431	$4,498

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (USD $)	3 Months Ended	0 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Apr. 27, 2015	Apr. 02, 2015
Subsequent Event [Line Items]
Dividend declared, date	2-Apr-15
Dividend paid, date	27-Apr-15
Dividend record, date	17-Apr-15
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend per common share			$0.75
Dividend paid		$26.60