Life Storage Inc - Registered Shares (LSI) 10-Q 4 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 23, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Trading Symbol	SSS
Entity Registrant Name	SOVRAN SELF STORAGE INC
Entity Central Index Key	944,314
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		36,168,440

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment in storage facilities:
Land	$ 478,872	$ 397,642
Building, equipment, and construction in progress	1,993,604	1,780,341
Real estate investment property, at cost, total	2,472,476	2,177,983
Less: accumulated depreciation	(451,117)	(411,701)
Investment in storage facilities, net	2,021,359	1,766,282
Cash and cash equivalents	6,067	8,543
Accounts receivable	6,480	5,758
Receivable from unconsolidated joint ventures	814	583
Investment in unconsolidated joint ventures	57,185	57,803
Prepaid expenses	5,766	6,533
Other assets	9,141	9,298
Total Assets	2,106,812	1,854,800
Liabilities
Line of credit	114,000	49,000
Term notes	750,000	750,000
Accounts payable and accrued liabilities	47,146	43,551
Deferred revenue	7,475	7,290
Fair value of interest rate swap agreements	19,426	13,341
Mortgages payable	2,028	2,127
Total Liabilities	940,075	865,309
Noncontrolling redeemable Operating Partnership Units at redemption value	16,698	13,622
Shareholders' Equity
Common stock $.01 par value, 100,000,000 shares authorized, 36,168,440 shares outstanding at September 30, 2015 (34,105,955 at December 31, 2014)	362	341
Additional paid-in capital	1,337,656	1,156,225
Dividends in excess of net income	(168,871)	(167,692)
Accumulated other comprehensive loss	(19,108)	(13,005)
Total Shareholders' Equity	1,150,039	975,869
Total Liabilities and Shareholders' Equity	$ 2,106,812	$ 1,854,800

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 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	36,168,440	34,105,955

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Rental income	$ 88,066	$ 79,092	$ 250,439	$ 223,438
Other operating income	7,362	6,157	21,124	17,712
Total operating revenues	95,428	85,249	271,563	241,150
Expenses
Property operations and maintenance	20,954	19,243	61,001	55,720
Real estate taxes	9,247	8,312	27,311	24,433
General and administrative	9,367	8,711	28,459	26,111
Acquisition costs	1,046	1,210	2,415	5,926
Operating leases of storage facilities		1,997	683	5,991
Depreciation and amortization	14,671	13,357	43,437	37,780
Total operating expenses	55,285	52,830	163,306	155,961
Income from operations	40,143	32,419	108,257	85,189
Other income (expenses)
Interest expense	(9,419)	(9,116)	(27,796)	(25,331)
Interest income	1	1	4	31
(Loss) gain on sale of storage facility		1,777	(7)	1,777
Equity in income of joint ventures	936	662	2,436	1,553
Net income	31,661	25,743	82,894	63,219
Net income attributable to noncontrolling interest	(157)	(154)	(407)	(381)
Net income attributable to common shareholders	$ 31,504	$ 25,589	$ 82,487	$ 62,838
Earnings per common share attributable to common shareholders - basic	$ 0.88	$ 0.77	$ 2.35	$ 1.92
Earnings per common share attributable to common shareholders - diluted	$ 0.88	$ 0.77	$ 2.33	$ 1.91
Common shares used in basic earnings per share calculation	35,700,375	33,234,660	35,135,946	32,806,164
Common shares used in diluted earnings per share calculation	35,917,105	33,398,648	35,358,332	32,972,262
Dividends declared per common share	$ 0.85	$ 0.68	$ 2.35	$ 2.04

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 31,661	$ 25,743	$ 82,894	$ 63,219
Other comprehensive income:
Change in fair value of derivatives net of reclassification to interest expense	(4,537)	2,464	(6,103)	(3,191)
Total comprehensive income	27,124	28,207	76,791	60,028
Comprehensive income attributable to noncontrolling interest	(135)	(170)	(377)	(362)
Comprehensive income attributable to common shareholders	$ 26,989	$ 28,037	$ 76,414	$ 59,666

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating Activities
Net income	$ 82,894	$ 63,219
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	43,437	37,780
Amortization of deferred financing fees	888	619
Loss (gain) on sale of storage facility	7	(1,777)
Equity in income of joint ventures	(2,436)	(1,553)
Distributions from unconsolidated joint ventures	3,250	2,280
Non-vested stock earned	4,786	3,540
Stock option expense	163	186
Changes in assets and liabilities (excluding the effects of acquisitions):
Accounts receivable	(715)	(514)
Prepaid expenses	776	(1,186)
(Advances to) receipts from joint ventures	(231)	252
Accounts payable and other liabilities	5,823	5,680
Deferred revenue	(589)	(894)
Net cash provided by operating activities	138,053	107,632
Investing Activities
Acquisitions of storage facilities	(273,469)	(229,709)
Improvements, equipment additions, and construction in progress	(24,332)	(20,257)
Net proceeds from the sale of storage facility	711	5,063
Investment in unconsolidated joint ventures	(483)	(9,383)
Property deposit	(1,215)	(776)
Net cash used in investing activities	(298,788)	(255,062)
Financing Activities
Net proceeds from sale of common stock	176,503	87,707
Proceeds from line of credit	297,000	125,000
Repayments of line of credit	(232,000)	(174,000)
Proceeds from term notes		175,000
Financing costs		(711)
Dividends paid-common stock	(82,742)	(67,113)
Distributions to noncontrolling interest holders	(403)	(406)
Mortgage principal payments	(99)	(95)
Net cash provided by financing activities	158,259	145,382
Net decrease in cash	(2,476)	(2,048)
Cash at beginning of period	8,543	9,524
Cash at end of period	6,067	7,476
Supplemental cash flow information
Cash paid for interest, net of interest capitalized	25,844	20,091
Cash paid for income taxes, net of refunds	$ 1,080	$ 895

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 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 nine month period ended September 30, 2015 are not necessarily indicative of the results that may be expected for the year ending December 31, 2015. Reclassification:

Organization

Organization	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [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 September 30, 2015, we had an ownership interest in, leased, and/or managed 539 self-storage properties in 25 states under the name Uncle Bob’s Self Storage ® 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 September 30, 2015. The remaining ownership interests in the Operating Partnership (the “Units”) are held by certain former owners of assets acquired by the Operating Partnership. 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 September 30, 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 (dollars in thousands) Nine Months 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 407 Distributions (403 ) Adjustment to redemption value 924 Ending balance noncontrolling redeemable Operating Partnership Units $ 16,698 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	9 Months Ended
	Sep. 30, 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 For the three months ended September 30, 2015 and 2014, the Company recorded compensation expense (included in general and administrative expense) of $46,000 and $37,000, respectively, related to stock options and $1,552,000 and $1,129,000, respectively, related to amortization of non-vested stock grants. For the nine months ended September 30, 2015 and 2014, the Company recorded compensation expense of $163,000 and $186,000, respectively, related to stock options and $4,743,000 and $3,451,000, respectively, related to amortization of non-vested stock grants. During the three months ended September 30, 2015 and 2014, employees and directors exercised 1,900 and 3,962 stock options respectively, and 31,078 and 31,078 shares of non-vested stock, respectively, vested. During the nine months ended September 30, 2015 and 2014, employees and directors exercised 16,900 and 12,962 stock options respectively, and 42,307 and 48,678 shares of non-vested stock, respectively, vested.

Investment in Storage Facilitie

Investment in Storage Facilities	9 Months Ended
	Sep. 30, 2015
Real Estate [Abstract]
Investment in Storage Facilities	4. INVESTMENT IN STORAGE FACILITIES The following summarizes our activity in storage facilities during the nine months ended September 30, 2015. (dollars in thousands) Cost: Beginning balance $ 2,177,983 Acquisition of storage facilities 272,148 Improvements and equipment additions 18,898 Net increase in construction in progress 5,586 Dispositions (2,139 ) Ending balance $ 2,472,476 Accumulated Depreciation: Beginning balance $ 411,701 Depreciation expense during the period 40,746 Dispositions (1,330 ) Ending balance $ 451,117 The Company acquired 26 facilities during the nine months ended September 30, 2015. 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 and three stores that were acquired at certificate of occupancy were accounted for as asset acquisitions. The cost of these seven stores was assigned to their land, building, equipment and improvements components based upon their fair values. The assets and liabilities of the other 19 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 (dollars in thousands) Consideration paid Acquisition Date Fair Value State Number of Date of Purchase Price Cash Paid Value of Net Other Land Building, In-Place Closing 2015 Connecticut 2 2/2/2015 $ 61,116 $ 62,377 $ — $ (1,261 ) $ 19,389 $ 41,727 $ — $ — New York 2 2/2/2015 57,900 59,103 — (1,203 ) 10,084 47,816 — — Illinois 1 2/5/2015 6,800 6,652 — 148 2,579 4,066 155 144 Illinois 1 3/9/2015 8,690 6,466 2,148 76 1,719 6,971 — — Florida 1 4/1/2015 6,290 6,236 — 54 1,793 4,382 115 357 Texas 1 4/16/2015 8,800 8,713 — 87 3,864 4,777 159 138 Florida 1 4/21/2015 8,750 8,687 — 63 2,118 6,501 131 120 Florida 4 5/1/2015 32,465 32,279 — 186 12,184 19,672 609 507 Arizona 1 6/16/2015 7,904 7,904 — — 852 7,052 — — Massachusetts 1 6/19/2015 10,291 10,286 — 5 2,110 8,181 — — New York 4 8/25/2015 17,900 17,690 — 210 4,685 12,826 389 400 North Carolina 1 9/1/2015 3,775 3,762 — 13 718 2,977 80 78 South Carolina 6 9/1/2015 44,000 43,564 — 436 17,461 25,644 895 671 Total acquired 2015 26 $ 274,681 $ 273,719 $ 2,148 $ (1,186 ) $ 79,556 $ 192,592 $ 2,533 $ 2,415 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 other 22 facilities have been included in the Company’s operations since the respective acquisition dates. Of the $273.7 million paid at closing for the properties acquired during the nine months ended September 30, 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 nine months ended September 30, 2015 include the issuance of $2.1 million in Operating Partnership Units, the assumption of $1.3 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: Sep. 30, Dec. 31, (Dollars in thousands) 2015 2014 In-place customer leases $ 22,305 $ 19,867 Accumulated amortization (20,335 ) (17,663 ) Net carrying value at the end of period $ 1,970 $ 2,204 Amortization expense related to in-place customer leases was $0.7 million and $1.2 million for the three months ended September 30, 2015 and 2014, respectively and was $2.7 million and $2.7 million for the nine months ended September 30, 2015 and 2014, respectively. The Company expects to record $3.4 million and $1.3 million of amortization expense for the years ended December 31, 2015 and 2016, respectively. During 2014, the Company acquired 33 properties. The following pro forma information is based on the combined historical financial statements of the Company and the 33 properties acquired, and presents the Company’s results as if the acquisitions had occurred as of January 1, 2013: Three months Nine months Total revenues $ 87,333 $ 251,322 Net income attributable to common shareholders $ 28,189 $ 70,380 Earnings per common share Basic $ 0.84 $ 2.09 Diluted $ 0.83 $ 2.08 Property Dispositions During the nine months ended September 30, 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. Jan. 1, 2015 Jan. 1, 2014 to to (Dollars in thousands) Sep. 30, 2015 Sep. 30, 2014 Total revenues $ 40 $ 91 Property operations and maintenance expense (16 ) (45 ) Real estate tax expense (5 ) (13 ) Depreciation and amortization expense (9 ) (18 ) Loss on sale of storage facilities (7 ) — $ 3 $ 15

Unsecured Line of Credit and Te

Unsecured Line of Credit and Term Notes	9 Months Ended
	Sep. 30, 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: Sep. 30, Dec. 31, (Dollars in thousands) 2015 2014 Revolving line of credit borrowings $ 114,000 $ 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 September 30, 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 September 30, 2015 the margin is 1.40%). The interest rate at September 30, 2015 on the Company’s line of credit was approximately 1.50% (1.46% at December 31, 2014). At September 30, 2015, there was $186 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 September 30, 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 September 30, 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 Matu

Mortgages Payable and Debt Maturities	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Mortgages Payable and Debt Maturities	6. MORTGAGES PAYABLE AND DEBT MATURITIES Mortgages payable at September 30, 2015 and December 31, 2014 consist of the following: (dollars in thousands) September 30, December 31, 5.99% mortgage notes due May 1, 2026, secured by one self-storage facility with an aggregate net book value of $4.3 million, principal and interest paid monthly (effective interest rate 6.23%) 2,028 2,127 Total mortgages payable $ 2,028 $ 2,127 The table below summarizes the Company’s debt obligations and interest rate derivatives at September 30, 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 Line of credit - variable rate LIBOR + 1.30% (1.50% at September 30, 2015) — — — — $ 114,000 — $ 114,000 $ 114,000 Notes Payable: Term note - fixed rate 6.38% — $ 150,000 — — — — $ 150,000 $ 156,962 Term note - variable rate LIBOR+1.40% (1.60% at September 30, 2015) — — — — — $ 325,000 $ 325,000 $ 325,000 Term note - fixed rate 5.54% — — — — — $ 100,000 $ 100,000 $ 111,988 Term note - fixed rate 4.533% — — — — — $ 175,000 $ 175,000 $ 175,295 Mortgage note - fixed rate 5.99% $ 34 $ 142 $ 151 $ 160 $ 170 $ 1,371 $ 2,028 $ 2,147 Interest rate derivatives - liability — — — — — — — $ 19,426

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 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 and nine months ended September 30, 2015, and 2014. The Company has interest rate swap agreements in effect at September 30, 2015 as detailed below to effectively convert a total of $325 million of variable-rate debt to fixed-rate debt. Notional Amount Effective Date Expiration Date Fixed Rate Paid Floating Rate Received $125 Million 9/1/2011 8/1/18 2.3700 % 1 month LIBOR $100 Million 12/30/11 12/29/17 1.6125 % 1 month LIBOR $100 Million 9/4/13 9/4/18 1.3710 % 1 month LIBOR $100 Million 12/29/17 11/29/19 3.9680 % 1 month LIBOR $125 Million 8/1/18 6/1/20 4.1930 % 1 month LIBOR The interest rate swap agreements are the only derivative instruments, as defined by FASB ASC Topic 815 “ Derivatives and Hedging 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 September 30, 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 September 30, 2015, it could have been required to settle its obligations under the agreements at their net termination cost of $19.4 million. The changes in AOCL for the three and nine months ended September 30, 2015 and September 30, 2014 are summarized as follows: (dollars in thousands) Jul. 1, 2015 Jul. 1, 2014 Jan. 1, 2015 Jan. 1, 2014 Accumulated other comprehensive loss beginning of period $ (14,571 ) $ (12,057 ) $ (13,005 ) $ (6,402 ) Realized loss reclassified from accumulated other comprehensive loss to interest expense 1,226 1,392 3,944 4,134 Unrealized loss from changes in the fair value of the effective portion of the interest rate swaps (5,763 ) 1,072 (10,047 ) (7,325 ) Loss included in other comprehensive loss (4,537 ) 2,464 (6,103 ) (3,191 ) Accumulated other comprehensive loss end of period $ (19,108 ) $ (9,593 ) $ (19,108 ) $ (9,593 )

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 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 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 September 30, 2015 and December 31, 2014 (in thousands): Asset Level 1 Level 2 Level 3 September 30, 2015 Interest rate swaps (19,426 ) — (19,426 ) — 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 26 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	9 Months Ended
	Sep. 30, 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 September 30, 2015 and December 31, 2014 was $44.8 million and $45.2 million, respectively. 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 to the joint venture as its share of capital required to fund acquisitions. As of September 30, 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 September 30, 2015 and December 31, 2014 was $12.4 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 $1.3 million and $1.0 million for the three months ended September 30, 2015 and 2014, respectively. The management and call center fees earned by the Company for the nine months ended September 30, 2015 and 2014, totaled $3.6 million and $2.8 million, respectively. The Company’s share of Sovran HHF and Sovran HHF II’s income for the three months ended September 30, 2015 and 2014 was $878,000 and $624,000, respectively. The Company’s share of Sovran HHF and Sovran HHF II’s income for the nine months ended September 30, 2015 and 2014 was $2,273,000 and $1,417,000, 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 September 30, 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 September 30, 2015, and 2014, the Company’s share of Iskalo Office Holdings, LLC’s income was $58,000 and $38,000, respectively. For the nine months ended September 30, 2015, and 2014, the Company’s share of Iskalo Office Holdings, LLC’s income was $162,000 and $102,000, respectively. The Company paid rent to Iskalo Office Holdings, LLC of $259,000 and $261,000 during the three months ended September 30, 2015 and 2014, respectively. The Company paid rent to Iskalo Office Holdings, LLC of $793,000 and $764,000 during the nine months ended September 30, 2015 and 2014, respectively. A summary of the unconsolidated joint ventures’ financial statements as of and for the nine months ended September 30, 2015 is as follows: (dollars in thousands) Sovran HHF Sovran HHF Iskalo Office Balance Sheet Data: Investment in storage facilities, net $ 336,935 $ 182,681 $ — Investment in office building — — 4,980 Other assets 8,071 5,014 3,308 Total Assets $ 345,006 $ 187,695 $ 8,288 Due to the Company $ 436 $ 391 $ — Mortgages payable 123,773 102,320 9,079 Other liabilities 5,395 2,484 404 Total Liabilities 129,604 105,195 9,483 Unaffiliated partners’ equity (deficiency) 172,322 70,131 (685 ) Company equity (deficiency) 43,080 12,369 (510 ) Total Partners’ Equity (Deficiency) 215,402 82,500 (1,195 ) Total Liabilities and Partners’ Equity (Deficiency) $ 345,006 $ 187,695 $ 8,288 Income Statement Data Total revenues $ 29,751 $ 22,385 $ 1,139 Property operating expenses (9,679 ) (7,619 ) (418 ) Administrative, management and call center fees (2,204 ) (1,656 ) — Depreciation and amortization of customer list (6,441 ) (3,153 ) (175 ) Income tax expense (132 ) (28 ) — Interest expense (4,384 ) (3,988 ) (215 ) Net income $ 6,911 $ 5,941 $ 331 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	9 Months Ended
	Sep. 30, 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 September 30, 2015 and 2014, the Company recorded federal and state income tax expense of $0.6 million and $0.4 million, respectively. For the nine months ended September 30, 2015 and 2014, the Company recorded federal and state income tax expense of $1.7 million and $1.2 million, respectively. At September 30, 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 September 30, 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 September 30, 2015, the Company’s taxable REIT subsidiary has a current tax liability of $0.6 million and a deferred tax liability of $1.2 million. The tax years 2012-2014 remain open to examination by the major taxing jurisdictions to which the Company is subject.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 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 Determining Whether Instruments Granted in Share-Based Payment Transactions Are Participating Securities” two-class (in thousands except per share data) Three Months Three Months Nine Months Nine Months Numerator: Net income attributable to common shareholders $ 31,504 $ 25,589 $ 82,487 $ 62,838 Denominator: Denominator for basic earnings per share – weighted average shares 35,700 33,235 35,136 32,806 Effect of Dilutive Securities: Stock options and non-vested stock 217 164 222 166 Denominator for diluted earnings per share – adjusted weighted average shares and assumed conversion 35,917 33,399 35,358 32,972 Basic earnings per common share attributable to common shareholders $ 0.88 $ 0.77 $ 2.35 $ 1.92 Diluted earnings per common share attributable to common shareholders $ 0.88 $ 0.77 $ 2.33 $ 1.91 Not included in the effect of dilutive securities above are 11,000 stock options and 139,518 unvested restricted shares for the three months ended September 30, 2015, and 6,000 stock options and 125,775 unvested restricted shares for the three months ended September 30, 2014, because their effect would be antidilutive. Not included in the effect of dilutive securities above are 7,333 stock options and 157,383 unvested restricted shares for the nine months ended September 30, 2015, and 6,667 stock options and 145,690 unvested restricted shares for the nine months ended September 30, 2014, because their effect would be antidilutive.

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 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) Nine Months Beginning balance of total shareholders’ equity $ 975,869 Net proceeds from the issuance of common stock 175,521 Exercise of stock options 982 Earned portion of non-vested stock 4,743 Stock option expense 163 Deferred compensation - directors 43 Adjustment to redemption value on noncontrolling redeemable Operating Partnership units (924 ) Net income attributable to common shareholders 82,487 Change in fair value of derivatives (6,103 ) Dividends (82,742 ) Ending balance of total shareholders’ equity $ 1,150,039 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 nine months ended September 30, 2015, 16,900 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 September 30, 2015, the Company issued 300,211 shares of common stock under the Equity Program at a weighted average issue price of $96.13 per share, generating net proceeds of $28.5 million after deducting $0.4 million of sales commissions paid to Piper. During the nine months ended September 30, 2015, the Company issued 499,911 shares of common stock under the Equity Program at a weighted average issue price of $94.29 per share, generating net proceeds of $46.5 million after deducting $0.6 million of sales commissions paid to Jefferies and Piper. The Company used the proceeds from the Equity Program to fund a portion of the acquisition of 26 storage facilities. As of September 30, 2015, the Company had $104.1 million available for issuance under the Equity Program. During the three months ended September 30, 2014, the Company issued 424,403 shares of common stock under the Equity Program at a weighted average issue price of $78.46 per share, generating net proceeds of $32.9 million after deducting $0.4 million of sales commissions paid to HSBC. During the nine months ended September 30, 2014, the Company issued 674,403 shares of common stock under the Equity Program at a weighted average issue price of $77.95 per share, generating net proceeds of $51.9 million after deducting $0.7 million of sales commissions paid to Piper and HSBC. 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 105,876 shares under the plan during the nine months ended September 30, 2015.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 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, 2017. 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. During April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, which amends the requirements for the presentation of debt issuance costs and requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. ASU No. 2015-03 is effective for fiscal years, beginning after December 15, 2015 and interim periods within those fiscal years. The implementation of this update is not expected to cause any material changes to our consolidated financial statements other than the reclassification of debt issuance costs from assets to a reduction of liabilities on our consolidated balance sheets. ASU No. 2015-03 was amended in August 2015 by ASU No. 2015-15, Interest - Imputation of Interest (Subtopic 835-30) - Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements, to add to the Codification SEC staff guidance that the SEC staff will not object to an entity presenting the costs of securing line-of-credit arrangements as an asset, regardless of whether there are any outstanding borrowings. The SEC Observer to the Emerging Issues Task Force announced the staff guidance in response to questions that arose after the FASB issued ASU No. 2015-03. In September 2015, the FASB issued ASU No. 2015-16, “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (“ASU 2015-16”). ASU 2015-16 requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. ASU 2015-16 is effective for fiscal years, and interim reporting periods within those fiscal years, beginning after December 15, 2015. The Company is still evaluating the impact that the adoption of ASU 2015-16 will have on its consolidated financial statements.

Commitment and Contingencies

Commitment and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitment and Contingencies	14. COMMITMENT AND CONTINGENCIES At September 30, 2015, the Company was under contract to acquire 9 self-storage facilities for cash consideration of approximately $66.7 million. The purchase of these 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 brought a motion to partially dismiss the complaint for failure to state a claim, and on July 16, 2015, the Company’s motion was granted in part and denied in part. The Company intends to vigorously defend the action, and the possibility of any adverse outcome cannot be determined at this time.

Reclassification

Reclassification	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [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 and nine months ended September 30, 2014 was $1,330 and $4,290, respectively (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 — 0.10 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 — 0.10 0.26 Earnings per share - diluted $ 2.67 $ 2.36 $ 1.87 From 1998 through 2003, the Company repurchased 1,171,886 common shares pursuant to a Share Repurchase Program authorized by the Company’s Board of Directors. These repurchased shares are subject to state corporate laws that establish the legal status of redeemed shares and prevent them from being reported as treasury shares within the consolidated financial statements. The Company previously misclassified the repurchased shares as treasury stock. The share repurchases should have been classified as reductions of common stock and additional paid-in capital. The accompanying consolidated balance sheet of the Company as of December 31, 2014 has been restated to correct the misclassification. The correction results in reductions in common shares and additional paid-in capital at December 31, 2014 of $11,719 and $27.2 million, respectively from the previously reported amounts of $353,000 and $1,183.4 million, respectively. The reclassification has no impact on the previously reported consolidated statements of operations or comprehensive income, nor does it have any effect on the previously reported consolidated statements of cash flows.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	16. SUBSEQUENT EVENTS On October 2, 2015, the Company declared a quarterly dividend of $0.85 per common share. The dividend was paid on October 26, 2015 to shareholders of record on October 16, 2015. The total dividend paid amounted to $30.6 million. On October 1, 2015, the Company entered into a joint venture agreement to develop a self storage facility in Florida. The Company has an 85% interest in the joint venture and is committed to funding up to $4.0 million of the development costs.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2015
Reclassification	Reclassification:
Fair Value Measurements and Disclosures	The assets and liabilities of the other 19 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, 2017. 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.
Debt Issuance Costs Associated with Line of Credit Arrangements	During April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, which amends the requirements for the presentation of debt issuance costs and requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. ASU No. 2015-03 is effective for fiscal years, beginning after December 15, 2015 and interim periods within those fiscal years. The implementation of this update is not expected to cause any material changes to our consolidated financial statements other than the reclassification of debt issuance costs from assets to a reduction of liabilities on our consolidated balance sheets.
Business Combinations	In September 2015, the FASB issued ASU No. 2015-16, “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments (“ASU 2015-16”). ASU 2015-16 requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. ASU 2015-16 is effective for fiscal years, and interim reporting periods within those fiscal years, beginning after December 15, 2015. The Company is still evaluating the impact that the adoption of ASU 2015-16 will have on its consolidated financial statements.
Line of Credit Arrangements [Member]
Debt Issuance Costs Associated with Line of Credit Arrangements	ASU No. 2015-03 was amended in August 2015 by ASU No. 2015-15, Interest - Imputation of Interest (Subtopic 835-30) - Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements, to add to the Codification SEC staff guidance that the SEC staff will not object to an entity presenting the costs of securing line-of-credit arrangements as an asset, regardless of whether there are any outstanding borrowings. The SEC Observer to the Emerging Issues Task Force announced the staff guidance in response to questions that arose after the FASB issued ASU No. 2015-03.

Organization (Tables)

Organization (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Redeemable Noncontrolling Interest	Redemption value exceeded the value determined under the Company’s historical basis of accounting at those dates. (dollars in thousands) Nine Months 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 407 Distributions (403 ) Adjustment to redemption value 924 Ending balance noncontrolling redeemable Operating Partnership Units $ 16,698

Investment in Storage Facilit25

Investment in Storage Facilities (Tables)	9 Months Ended
	Sep. 30, 2015
Real Estate [Abstract]
Summary of Activity in Storage Facilities	The following summarizes our activity in storage facilities during the nine months ended September 30, 2015. (dollars in thousands) Cost: Beginning balance $ 2,177,983 Acquisition of storage facilities 272,148 Improvements and equipment additions 18,898 Net increase in construction in progress 5,586 Dispositions (2,139 ) Ending balance $ 2,472,476 Accumulated Depreciation: Beginning balance $ 411,701 Depreciation expense during the period 40,746 Dispositions (1,330 ) Ending balance $ 451,117
Schedule of Acquired Facilities and Purchase Price of Facilities	The purchase price of the 26 facilities has been assigned as follows: (dollars in thousands) Consideration paid Acquisition Date Fair Value State Number of Date of Purchase Price Cash Paid Value of Net Other Land Building, In-Place Closing 2015 Connecticut 2 2/2/2015 $ 61,116 $ 62,377 $ — $ (1,261 ) $ 19,389 $ 41,727 $ — $ — New York 2 2/2/2015 57,900 59,103 — (1,203 ) 10,084 47,816 — — Illinois 1 2/5/2015 6,800 6,652 — 148 2,579 4,066 155 144 Illinois 1 3/9/2015 8,690 6,466 2,148 76 1,719 6,971 — — Florida 1 4/1/2015 6,290 6,236 — 54 1,793 4,382 115 357 Texas 1 4/16/2015 8,800 8,713 — 87 3,864 4,777 159 138 Florida 1 4/21/2015 8,750 8,687 — 63 2,118 6,501 131 120 Florida 4 5/1/2015 32,465 32,279 — 186 12,184 19,672 609 507 Arizona 1 6/16/2015 7,904 7,904 — — 852 7,052 — — Massachusetts 1 6/19/2015 10,291 10,286 — 5 2,110 8,181 — — New York 4 8/25/2015 17,900 17,690 — 210 4,685 12,826 389 400 North Carolina 1 9/1/2015 3,775 3,762 — 13 718 2,977 80 78 South Carolina 6 9/1/2015 44,000 43,564 — 436 17,461 25,644 895 671 Total acquired 2015 26 $ 274,681 $ 273,719 $ 2,148 $ (1,186 ) $ 79,556 $ 192,592 $ 2,533 $ 2,415
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: Sep. 30, Dec. 31, (Dollars in thousands) 2015 2014 In-place customer leases $ 22,305 $ 19,867 Accumulated amortization (20,335 ) (17,663 ) Net carrying value at the end of period $ 1,970 $ 2,204
Pro Forma Information Based on Combined Historical Financial Statements on Properties Acquired	The following pro forma information is based on the combined historical financial statements of the Company and the 33 properties acquired, and presents the Company’s results as if the acquisitions had occurred as of January 1, 2013: Three months Nine months Total revenues $ 87,333 $ 251,322 Net income attributable to common shareholders $ 28,189 $ 70,380 Earnings per common share Basic $ 0.84 $ 2.09 Diluted $ 0.83 $ 2.08
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. Jan. 1, 2015 Jan. 1, 2014 to to (Dollars in thousands) Sep. 30, 2015 Sep. 30, 2014 Total revenues $ 40 $ 91 Property operations and maintenance expense (16 ) (45 ) Real estate tax expense (5 ) (13 ) Depreciation and amortization expense (9 ) (18 ) Loss on sale of storage facilities (7 ) — $ 3 $ 15

Unsecured Line of Credit and 26

Unsecured Line of Credit and Term Notes (Tables)	9 Months Ended
	Sep. 30, 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: Sep. 30, Dec. 31, (Dollars in thousands) 2015 2014 Revolving line of credit borrowings $ 114,000 $ 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 Ma27

Mortgages Payable and Debt Maturities (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Summary of Mortgage Payable	Mortgages payable at September 30, 2015 and December 31, 2014 consist of the following: (dollars in thousands) September 30, December 31, 5.99% mortgage notes due May 1, 2026, secured by one self-storage facility with an aggregate net book value of $4.3 million, principal and interest paid monthly (effective interest rate 6.23%) 2,028 2,127 Total mortgages payable $ 2,028 $ 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 Line of credit - variable rate LIBOR + 1.30% (1.50% at September 30, 2015) — — — — $ 114,000 — $ 114,000 $ 114,000 Notes Payable: Term note - fixed rate 6.38% — $ 150,000 — — — — $ 150,000 $ 156,962 Term note - variable rate LIBOR+1.40% (1.60% at September 30, 2015) — — — — — $ 325,000 $ 325,000 $ 325,000 Term note - fixed rate 5.54% — — — — — $ 100,000 $ 100,000 $ 111,988 Term note - fixed rate 4.533% — — — — — $ 175,000 $ 175,000 $ 175,295 Mortgage note - fixed rate 5.99% $ 34 $ 142 $ 151 $ 160 $ 170 $ 1,371 $ 2,028 $ 2,147 Interest rate derivatives - liability — — — — — — — $ 19,426

Derivative Financial Instrume28

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of Interest Rate Swap Agreements	The Company has interest rate swap agreements in effect at September 30, 2015 as detailed below to effectively convert a total of $325 million of variable-rate debt to fixed-rate debt. Notional Amount Effective Date Expiration Date Fixed Rate Paid Floating Rate Received $125 Million 9/1/2011 8/1/18 2.3700 % 1 month LIBOR $100 Million 12/30/11 12/29/17 1.6125 % 1 month LIBOR $100 Million 9/4/13 9/4/18 1.3710 % 1 month LIBOR $100 Million 12/29/17 11/29/19 3.9680 % 1 month LIBOR $125 Million 8/1/18 6/1/20 4.1930 % 1 month LIBOR
Summary of Changes in AOCL	The changes in AOCL for the three and nine months ended September 30, 2015 and September 30, 2014 are summarized as follows: (dollars in thousands) Jul. 1, 2015 Jul. 1, 2014 Jan. 1, 2015 Jan. 1, 2014 Accumulated other comprehensive loss beginning of period $ (14,571 ) $ (12,057 ) $ (13,005 ) $ (6,402 ) Realized loss reclassified from accumulated other comprehensive loss to interest expense 1,226 1,392 3,944 4,134 Unrealized loss from changes in the fair value of the effective portion of the interest rate swaps (5,763 ) 1,072 (10,047 ) (7,325 ) Loss included in other comprehensive loss (4,537 ) 2,464 (6,103 ) (3,191 ) Accumulated other comprehensive loss end of period $ (19,108 ) $ (9,593 ) $ (19,108 ) $ (9,593 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2015 and December 31, 2014 (in thousands): Asset Level 1 Level 2 Level 3 September 30, 2015 Interest rate swaps (19,426 ) — (19,426 ) — December 31, 2014 Interest rate swaps (13,341 ) — (13,341 ) —

Investment in Joint Ventures (T

Investment in Joint Ventures (Tables)	9 Months Ended
	Sep. 30, 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 nine months ended September 30, 2015 is as follows: (dollars in thousands) Sovran HHF Sovran HHF Iskalo Office Balance Sheet Data: Investment in storage facilities, net $ 336,935 $ 182,681 $ — Investment in office building — — 4,980 Other assets 8,071 5,014 3,308 Total Assets $ 345,006 $ 187,695 $ 8,288 Due to the Company $ 436 $ 391 $ — Mortgages payable 123,773 102,320 9,079 Other liabilities 5,395 2,484 404 Total Liabilities 129,604 105,195 9,483 Unaffiliated partners’ equity (deficiency) 172,322 70,131 (685 ) Company equity (deficiency) 43,080 12,369 (510 ) Total Partners’ Equity (Deficiency) 215,402 82,500 (1,195 ) Total Liabilities and Partners’ Equity (Deficiency) $ 345,006 $ 187,695 $ 8,288 Income Statement Data Total revenues $ 29,751 $ 22,385 $ 1,139 Property operating expenses (9,679 ) (7,619 ) (418 ) Administrative, management and call center fees (2,204 ) (1,656 ) — Depreciation and amortization of customer list (6,441 ) (3,153 ) (175 ) Income tax expense (132 ) (28 ) — Interest expense (4,384 ) (3,988 ) (215 ) Net income $ 6,911 $ 5,941 $ 331

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 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 (in thousands except per share data) Three Months Three Months Nine Months Nine Months Numerator: Net income attributable to common shareholders $ 31,504 $ 25,589 $ 82,487 $ 62,838 Denominator: Denominator for basic earnings per share – weighted average shares 35,700 33,235 35,136 32,806 Effect of Dilutive Securities: Stock options and non-vested stock 217 164 222 166 Denominator for diluted earnings per share – adjusted weighted average shares and assumed conversion 35,917 33,399 35,358 32,972 Basic earnings per common share attributable to common shareholders $ 0.88 $ 0.77 $ 2.35 $ 1.92 Diluted earnings per common share attributable to common shareholders $ 0.88 $ 0.77 $ 2.33 $ 1.91

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 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) Nine Months Beginning balance of total shareholders’ equity $ 975,869 Net proceeds from the issuance of common stock 175,521 Exercise of stock options 982 Earned portion of non-vested stock 4,743 Stock option expense 163 Deferred compensation - directors 43 Adjustment to redemption value on noncontrolling redeemable Operating Partnership units (924 ) Net income attributable to common shareholders 82,487 Change in fair value of derivatives (6,103 ) Dividends (82,742 ) Ending balance of total shareholders’ equity $ 1,150,039

Reclassification (Tables)

Reclassification (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [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 — 0.10 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 — 0.10 0.26 Earnings per share - diluted $ 2.67 $ 2.36 $ 1.87

Organization - Additional Infor

Organization - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2015USD ($)Facilityshares	Sep. 30, 2015USD ($)StatesPropertyshares	Dec. 31, 2014shares	Dec. 31, 2012Property	Dec. 31, 2011Property	Dec. 31, 2008Property
Organization [Line Items]
Number of self-storage properties owned and managed		539
Number of states in which self-storage properties owned and managed | States		25
Number of properties managed with no ownership		17
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 | shares		178,866	155,484
Noncontrolling limited partnership unit redemption value		One common share or cash
Number of units issued for acquisition | shares	23,382
Fair value of units, issued for acquisition | $	$ 2.1	$ 2.1
Number of self storage properties acquired | Facility	1
Sovran HHF Storage Holdings LLC [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]
Organization [Line Items]
Percentage of variable interest 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		41.00%
Geographic Concentration Risk [Member] | Houston Texas [Member] | Revenue [Member]
Organization [Line Items]
Concentration risk, percentage		11.00%

Organization - Summary of Redee

Organization - Summary of Redeemable Noncontrolling Interest (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 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	$ 157	$ 154	407	$ 381	$ 526	$ 469	$ 513
Distributions			(403)	$ (406)
Adjustment to redemption value			924
Ending balance noncontrolling redeemable Operating Partnership Units	$ 16,698		$ 16,698		$ 13,622

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock option expense	$ 46	$ 37	$ 163	$ 186
Amortization of non-vested stock grants	$ 1,552	$ 1,129	$ 4,743	$ 3,451
Stock options exercised by employees and directors	1,900	3,962	16,900	12,962
Number of shares of non-vested stock that vested	31,078	31,078	42,307	48,678

Investment in Storage Facilit37

Investment in Storage Facilities - Summary of Activity in Storage Facilities (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)
Cost:
Beginning balance	$ 2,177,983
Acquisition of storage facilities	272,148
Improvements and equipment additions	18,898
Net increase in construction in progress	5,586
Dispositions	(2,139)
Ending balance	2,472,476
Accumulated Depreciation:
Beginning balance	411,701
Depreciation expense during the period	40,746
Dispositions	(1,330)
Ending balance	$ 451,117

Investment in Storage Facilit38

Investment in Storage Facilities - Additional Information (Detail)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)Facility	Mar. 31, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)FacilityPropertyStore	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)Facility	Feb. 02, 2015Facility
Investment Holdings [Line Items]
Number of storage facilities acquired | Facility				26		33
Stores acquired at certificate of occupancy | Store				3
Number of facilities acquired included in operations | Facility	22			22
Cash paid for properties acquired				$ 273,700,000
Deposits paid at the time of contract	$ 250,000			250,000
Issuance of Operating Partnership Units		$ 2,100,000		2,100,000
Net other liabilities assumed				1,300,000
Settlement of a straight-line rent liability				$ 2,400,000
Amortization period for in-place customer leases on a straight-line basis				12 months
Amortization expense related to in-place customer leases	700,000		$ 1,200,000	$ 2,700,000	$ 2,700,000
Amortization expense expected for 2015	3,400,000			3,400,000
Amortization expense expected for 2016	1,300,000			$ 1,300,000
Number of properties sold | Property				1
Carrying value of properties sold	$ 698,000			$ 698,000
Net proceeds from the sale of storage facility				711,000	5,063,000
Loss on sale of storage facilities			$ 1,777,000	(7,000)	$ 1,777,000	$ 5,176,000
Connecticut and New York [Member]
Investment Holdings [Line Items]
Number of facilities acquired and leased since November 1, 2013 | Facility							4
One Property [Member]
Investment Holdings [Line Items]
Net proceeds from the sale of storage facility				$ 691,000

Investment in Storage Facilit39

Investment in Storage Facilities - Schedule of Acquired Facilities and Purchase Price of Facilities (Detail) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)FacilityProperty	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)Facility	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)
Investment Holdings [Line Items]
Number of Properties | Facility			26		33
Cash Paid			$ 273,700
Closing Costs Expensed	$ 1,046	$ 1,210	$ 2,415	$ 5,926	$ 7,359	$ 3,129	$ 4,328
Acquisitions 2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			26
Purchase Price	274,681		$ 274,681
Cash Paid			273,719
Consideration paid Value of Operating Partnership Units Issued			2,148
Net Other Liabilities (Assets) Assumed	(1,186)		(1,186)
Land	79,556		79,556
Acquisition Date Building, Equipment, and Improvements	192,592		192,592
Fair Value In-Place Customers Leases	2,533		2,533
Closing Costs Expensed			$ 2,415
Connecticut [Member] | Date of Acquisition, 2/2/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			2
Date of Acquisition			Feb. 2, 2015
Purchase Price	61,116		$ 61,116
Cash Paid			62,377
Net Other Liabilities (Assets) Assumed	(1,261)		(1,261)
Land	19,389		19,389
Acquisition Date Building, Equipment, and Improvements	41,727		$ 41,727
New York [Member] | Date of Acquisition, 2/2/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			2
Date of Acquisition			Feb. 2, 2015
Purchase Price	57,900		$ 57,900
Cash Paid			59,103
Net Other Liabilities (Assets) Assumed	(1,203)		(1,203)
Land	10,084		10,084
Acquisition Date Building, Equipment, and Improvements	47,816		$ 47,816
New York [Member] | Date of Acquisition, 8/25/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			4
Date of Acquisition			Aug. 25, 2015
Purchase Price	17,900		$ 17,900
Cash Paid			17,690
Net Other Liabilities (Assets) Assumed	210		210
Land	4,685		4,685
Acquisition Date Building, Equipment, and Improvements	12,826		12,826
Fair Value In-Place Customers Leases	389		389
Closing Costs Expensed			$ 400
Illinois [Member] | Date of Acquisition, 2/5/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Feb. 5, 2015
Purchase Price	6,800		$ 6,800
Cash Paid			6,652
Net Other Liabilities (Assets) Assumed	148		148
Land	2,579		2,579
Acquisition Date Building, Equipment, and Improvements	4,066		4,066
Fair Value In-Place Customers Leases	155		155
Closing Costs Expensed			$ 144
Illinois [Member] | Date of Acquisition, 3/9/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Mar. 9, 2015
Purchase Price	8,690		$ 8,690
Cash Paid			6,466
Consideration paid Value of Operating Partnership Units Issued			2,148
Net Other Liabilities (Assets) Assumed	76		76
Land	1,719		1,719
Acquisition Date Building, Equipment, and Improvements	6,971		$ 6,971
Florida [Member] | Date of Acquisition, 4/1/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Apr. 1, 2015
Purchase Price	6,290		$ 6,290
Cash Paid			6,236
Net Other Liabilities (Assets) Assumed	54		54
Land	1,793		1,793
Acquisition Date Building, Equipment, and Improvements	4,382		4,382
Fair Value In-Place Customers Leases	115		115
Closing Costs Expensed			$ 357
Florida [Member] | Date of Acquisition, 4/21/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Apr. 21, 2015
Purchase Price	8,750		$ 8,750
Cash Paid			8,687
Net Other Liabilities (Assets) Assumed	63		63
Land	2,118		2,118
Acquisition Date Building, Equipment, and Improvements	6,501		6,501
Fair Value In-Place Customers Leases	131		131
Closing Costs Expensed			$ 120
Florida [Member] | Date of Acquisition, 5/1/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			4
Date of Acquisition			May 1, 2015
Purchase Price	32,465		$ 32,465
Cash Paid			32,279
Net Other Liabilities (Assets) Assumed	186		186
Land	12,184		12,184
Acquisition Date Building, Equipment, and Improvements	19,672		19,672
Fair Value In-Place Customers Leases	609		609
Closing Costs Expensed			$ 507
Texas [Member] | Date of Acquisition, 4/16/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Apr. 16, 2015
Purchase Price	8,800		$ 8,800
Cash Paid			8,713
Net Other Liabilities (Assets) Assumed	87		87
Land	3,864		3,864
Acquisition Date Building, Equipment, and Improvements	4,777		4,777
Fair Value In-Place Customers Leases	159		159
Closing Costs Expensed			$ 138
Arizona [Member] | Date of Acquisition, 6/16/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Jun. 16, 2015
Purchase Price	7,904		$ 7,904
Cash Paid			7,904
Land	852		852
Acquisition Date Building, Equipment, and Improvements	7,052		$ 7,052
Massachusetts [Member] | Date of Acquisition, 6/19/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Jun. 19, 2015
Purchase Price	10,291		$ 10,291
Cash Paid			10,286
Net Other Liabilities (Assets) Assumed	5		5
Land	2,110		2,110
Acquisition Date Building, Equipment, and Improvements	8,181		$ 8,181
North Carolina [Member] | Date of Acquisition, 9/1/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			1
Date of Acquisition			Sep. 1, 2015
Purchase Price	3,775		$ 3,775
Cash Paid			3,762
Net Other Liabilities (Assets) Assumed	13		13
Land	718		718
Acquisition Date Building, Equipment, and Improvements	2,977		2,977
Fair Value In-Place Customers Leases	80		80
Closing Costs Expensed			$ 78
South Carolina [Member] | Date of Acquisition, 9/1/2015 [Member]
Investment Holdings [Line Items]
Number of Properties | Property			6
Date of Acquisition			Sep. 1, 2015
Purchase Price	44,000		$ 44,000
Cash Paid			43,564
Net Other Liabilities (Assets) Assumed	436		436
Land	17,461		17,461
Acquisition Date Building, Equipment, and Improvements	25,644		25,644
Fair Value In-Place Customers Leases	$ 895		895
Closing Costs Expensed			$ 671

Investment in Storage Facilit40

Investment in Storage Facilities - Schedule of Fair Value of In-Place Customer Lease Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Real Estate [Abstract]
In-place customer leases	$ 22,305	$ 19,867
Accumulated amortization	(20,335)	(17,663)
Net carrying value at the end of period	$ 1,970	$ 2,204

Investment in Storage Facilit41

Investment in Storage Facilities - Pro Forma Information Based on Combined Historical Financial Statements on Properties Acquired (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014
Investments Schedule [Abstract]
Total revenues	$ 87,333	$ 251,322
Net income attributable to common shareholders	$ 28,189	$ 70,380
Basic	$ 0.84	$ 2.09
Diluted	$ 0.83	$ 2.08

Investment in Storage Facilit42

Investment in Storage Facilities - Summary of Revenues and Expenses Related to Sale of Properties Included in Company's Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 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	$ 95,428	$ 85,249	$ 271,563	$ 241,150	$ 326,080	$ 273,507	$ 234,082
Property operations and maintenance expense	(20,954)	(19,243)	(61,001)	(55,720)	(75,333)	(66,119)	(59,011)
Real estate tax expense	(9,247)	(8,312)	(27,311)	(24,433)	(32,097)	(26,496)	(22,076)
Depreciation and amortization expense	$ (14,671)	(13,357)	(43,437)	(37,780)	(51,749)	$ (45,233)	$ (40,542)
Loss on sale of storage facilities		$ 1,777	(7)	1,777	$ 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	91
Property operations and maintenance expense			(16)	(45)
Real estate tax expense			(5)	(13)
Depreciation and amortization expense			(9)	(18)
Loss on sale of storage facilities			(7)
Total income from discontinued operations			$ 3	$ 15

Unsecured Line of Credit and 43

Unsecured Line of Credit and Term Notes - Borrowings Outstanding on Unsecured Line of Credit and Term Notes (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Unsecured Line Of Credit And Term Notes [Line Items]
Revolving line of credit borrowings	$ 114,000	$ 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 44

Unsecured Line of Credit and Term Notes - Additional Information (Detail) - USD ($)	Apr. 08, 2014	Sep. 30, 2015	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
Maturity on December 10, 2019 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Facility fee		0.20%
Interest rate, line of credit facility		1.50%		1.46%
Amount available on unsecured line of credit		$ 186,000,000
Line of credit facility, expiration date		Dec. 10, 2019
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
Line of Credit - Variable Rate LIBOR + 1.30% (1.50% at September 30, 2015) [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Basis spread over LIBOR		1.30%
Interest rate, line of credit facility		1.50%
Line of Credit - Variable Rate LIBOR + 1.30% (1.50% at September 30, 2015) [Member] | Maturity on June 4, 2020 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Basis spread over LIBOR		1.40%
Line of Credit - Variable Rate LIBOR + 1.30% (1.50% at September 30, 2015) [Member] | Maturity on December 10, 2019 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Basis spread over LIBOR		1.30%
Maturity in April, 2024 [Member]
Unsecured Line Of Credit And Term Notes [Line Items]
Line of credit facility, expiration date		Apr. 8, 2024
Additional secured term note	$ 175,000,000
Term note stated interest rate		4.533%
Increase in interest rate on term loan		6.283%
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		Aug. 5, 2021
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		Apr. 13, 2016
Term note stated interest rate		6.38%
Increase in interest rate on term loan		8.13%

Mortgages Payable and Debt Ma45

Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Mortgages payable	$ 2,028	$ 2,127
5.99% Mortgage Notes Due May 1, 2026 [Member]
Debt Instrument [Line Items]
Mortgages payable	$ 2,028	$ 2,127

Mortgages Payable and Debt Ma46

Mortgages Payable and Debt Maturities - Summary of Mortgage Payable (Parenthetical) (Detail) - 5.99% Mortgage Notes Due May 1, 2026 [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)Facility
Debt Instrument [Line Items]
Interest rate	5.99%
Mortgage note due date	May 1, 2026
Self-storage facilities	1
Aggregate net book value of property pledged for mortgage note | $	$ 4.3
Effective interest rate	6.23%

Mortgages Payable and Debt Ma47

Mortgages Payable and Debt Maturities - Summary of Debt Obligation and Interest Rate Derivatives (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Line of credit	$ 114,000	$ 49,000
Term notes	750,000	750,000
Mortgage note, total	2,028	2,127
Interest rate derivatives - liability	19,426	$ 13,341
Line of Credit - Variable Rate LIBOR + 1.30% (1.50% at September 30, 2015) [Member]
Debt Instrument [Line Items]
Payable due 2019	114,000
Line of credit	114,000
Debt instrument, fair value	114,000
Term Note - Fixed Rate 6.38% [Member]
Debt Instrument [Line Items]
Payables due 2016	150,000
Term notes	150,000
Term note, fair value	156,962
Term Note - Variable Rate LIBOR+1.40% (1.60% at September 30, 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	111,988
Term Note - Fixed Rate 4.533% [Member]
Debt Instrument [Line Items]
Payables due Thereafter	175,000
Term notes	175,000
Term note, fair value	175,295
Mortgage Note - Fixed Rate 5.99% [Member]
Debt Instrument [Line Items]
Payable due 2015	34
Payables due 2016	142
Payables due 2017	151
Payable due 2018	160
Payable due 2019	170
Payables due Thereafter	1,371
Mortgage note, total	2,028
Debt instrument, fair value	$ 2,147

Mortgages Payable and Debt Ma48

Mortgages Payable and Debt Maturities - Summary of Debt Obligation and Interest Rate Derivatives (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2015
Line of Credit - Variable Rate LIBOR + 1.30% (1.50% at September 30, 2015) [Member]
Debt Instrument [Line Items]
Interest rate at end of period	1.50%
Basis spread over LIBOR	1.30%
Term Note - Fixed Rate 6.38% [Member]
Debt Instrument [Line Items]
Interest rate	6.38%
Term Note - Variable Rate LIBOR+1.40% (1.60% at September 30, 2015) [Member]
Debt Instrument [Line Items]
Interest rate	1.60%
Basis spread over LIBOR	1.40%
Term Note - Fixed Rate 5.54% [Member]
Debt Instrument [Line Items]
Interest rate	5.54%
Term Note - Fixed Rate 4.533% [Member]
Debt Instrument [Line Items]
Interest rate	4.533%
Mortgage Note - Fixed Rate 5.99% [Member]
Debt Instrument [Line Items]
Interest rate	5.99%

Derivative Financial Instrume49

Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2016	Dec. 31, 2014
Derivative [Line Items]
Realized loss reclassified from accumulated other comprehensive loss to interest expense	$ (1,226)	$ (1,392)	$ (3,944)	$ (4,134)
Fair value of interest rate swap agreements	19,426		19,426			$ 13,341
Net termination cost	19,400		19,400
Interest Expense [Member]
Derivative [Line Items]
Realized loss reclassified from accumulated other comprehensive loss to interest expense	1,200	$ 1,400	3,900	$ 4,100
Scenario, Forecast [Member]
Derivative [Line Items]
Estimated payments to be made under interest rate swaps					$ 5,400
Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount of variable rate debt swapped	$ 325,000		$ 325,000

Derivative Financial Instrume50

Derivative Financial Instruments - Summary of Interest Rate Swap Agreements (Detail)	9 Months Ended
	Sep. 30, 2015USD ($)
Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	$ 125,000,000
Effective Date	Sep. 1, 2011
Expiration Date	Aug. 1, 2018
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	Dec. 30, 2011
Expiration Date	Dec. 29, 2017
Fixed Rate Paid	1.6125%
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	Sep. 4, 2013
Expiration Date	Sep. 4, 2018
Fixed Rate Paid	1.371%
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	Dec. 29, 2017
Expiration Date	Nov. 29, 2019
Fixed Rate Paid	3.968%
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	Aug. 1, 2018
Expiration Date	Jun. 1, 2020
Fixed Rate Paid	4.193%
Interest Rate Swap Four [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Floating Rate Received	1 month LIBOR

Derivative Financial Instrume51

Derivative Financial Instruments - Summary of Changes in AOCL (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Accumulated other comprehensive loss beginning of period	$ (14,571)	$ (12,057)	$ (13,005)	$ (6,402)
Realized loss reclassified from accumulated other comprehensive loss to interest expense	1,226	1,392	3,944	4,134
Unrealized loss from changes in the fair value of the effective portion of the interest rate swaps	(5,763)	1,072	(10,047)	(7,325)
Loss included in other comprehensive loss	(4,537)	2,464	(6,103)	(3,191)
Accumulated other comprehensive loss end of period	$ (19,108)	$ (9,593)	$ (19,108)	$ (9,593)

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Carried at Fair Value Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Interest rate swaps	$ (19,426)	$ (13,341)
Interest Rate Swap [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Interest rate swaps	(19,426)	(13,341)
Interest Rate Swap [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Interest rate swaps	$ (19,426)	$ (13,341)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - Facility	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Number of storage facilities acquired	26	33
Storage Facilities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Number of storage facilities acquired	26

Investment in Joint Ventures -

Investment in Joint Ventures - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)Property	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)Property	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)Property	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)Property	Dec. 31, 2011USD ($)Property	Dec. 31, 2008USD ($)Property
Schedule of Equity Method Investments [Line Items]
Investment at carrying value	$ 57,185,000		$ 57,185,000		$ 57,803,000
Equity in income of joint ventures	936,000	$ 662,000	2,436,000	$ 1,553,000	2,086,000	$ 1,948,000	$ 936,000
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Investment at carrying value	$ 12,400,000		$ 12,400,000		12,600,000
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
Percentage of variable interest ownership in unconsolidated joint venture			15.00%
Number of properties owned and managed under fifteen-percent stake joint venture | Property	30		30				10	20
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Percentage ownership in unconsolidated joint venture	20.00%		20.00%
Investment at carrying value	$ 44,800,000		$ 44,800,000		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 | Property	39		39						25
Additional number of properties owned and managed under twenty-percent stake joint venture | Property					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		$ 1,700,000
Other-than-temporary impairment recorded on investment			0
Sovran HHF and Sovran HHF II [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	$ 1,300,000	1,000,000	3,600,000	2,800,000
Equity in income of joint ventures	$ 878,000	624,000	$ 2,273,000	1,417,000
Iskalo Office Holdings, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Percentage ownership in unconsolidated joint venture	49.00%		49.00%
Equity in income of joint ventures	$ 58,000	38,000	$ 162,000	102,000
Investment liability at carrying value	(500,000)		(500,000)		$ (500,000)
Rent paid during the period	$ 259,000	$ 261,000	$ 793,000	$ 764,000

Investment in Joint Ventures 55

Investment in Joint Ventures - Summary of Unconsolidated Joint Ventures' Financial Statements (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Investment in storage facilities, net	$ 2,021,359		$ 2,021,359		$ 1,766,282
Other assets	9,141		9,141		9,298
Total Assets	2,106,812		2,106,812		1,854,800
Mortgages payable	2,028		2,028		2,127
Total Liabilities	940,075		940,075		865,309
Company equity (deficiency)	1,150,039		1,150,039		975,869
Depreciation and amortization of customer list	(14,671)	$ (13,357)	(43,437)	$ (37,780)	(51,749)	$ (45,233)	$ (40,542)
Income tax expense	(600)	(400)	(1,700)	(1,200)
Interest expense	(9,419)	$ (9,116)	(27,796)	$ (25,331)	$ (34,578)	$ (32,000)	$ (33,166)
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Investment in storage facilities, net	336,935		336,935
Other assets	8,071		8,071
Total Assets	345,006		345,006
Due to the Company	436		436
Mortgages payable	123,773		123,773
Other liabilities	5,395		5,395
Total Liabilities	129,604		129,604
Unaffiliated partners' equity (deficiency)	172,322		172,322
Company equity (deficiency)	43,080		43,080
Total Partners' Equity (Deficiency)	215,402		215,402
Total Liabilities and Partners' Equity (Deficiency)	345,006		345,006
Total revenues			29,751
Property operating expenses			(9,679)
Administrative, management and call center fees			(2,204)
Depreciation and amortization of customer list			(6,441)
Income tax expense			(132)
Interest expense			(4,384)
Net income			6,911
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Investment in storage facilities, net	182,681		182,681
Other assets	5,014		5,014
Total Assets	187,695		187,695
Due to the Company	391		391
Mortgages payable	102,320		102,320
Other liabilities	2,484		2,484
Total Liabilities	105,195		105,195
Unaffiliated partners' equity (deficiency)	70,131		70,131
Company equity (deficiency)	12,369		12,369
Total Partners' Equity (Deficiency)	82,500		82,500
Total Liabilities and Partners' Equity (Deficiency)	187,695		187,695
Total revenues			22,385
Property operating expenses			(7,619)
Administrative, management and call center fees			(1,656)
Depreciation and amortization of customer list			(3,153)
Income tax expense			(28)
Interest expense			(3,988)
Net income			5,941
Iskalo Office Holdings, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Investment in office building	4,980		4,980
Other assets	3,308		3,308
Total Assets	8,288		8,288
Mortgages payable	9,079		9,079
Other liabilities	404		404
Total Liabilities	9,483		9,483
Unaffiliated partners' equity (deficiency)	(685)		(685)
Company equity (deficiency)	(510)		(510)
Total Partners' Equity (Deficiency)	(1,195)		(1,195)
Total Liabilities and Partners' Equity (Deficiency)	$ 8,288		8,288
Total revenues			1,139
Property operating expenses			(418)
Depreciation and amortization of customer list			(175)
Interest expense			(215)
Net income			$ 331

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Federal and state income tax expense	$ 600,000	$ 400,000	$ 1,700,000	$ 1,200,000
Unrecognized tax benefits	0	$ 0	0	0
Interest or penalties related to uncertain tax positions			0	$ 0
Current tax liability	600,000		600,000
Deferred tax liability	$ 1,200,000		$ 1,200,000
Tax years open to examination			2012-2014

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income attributable to common shareholders	$ 31,504	$ 25,589	$ 82,487	$ 62,838	$ 88,531	$ 74,126	$ 55,128
Denominator:
Denominator for basic earnings per share - weighted average shares	35,700,375	33,234,660	35,135,946	32,806,164
Effect of Dilutive Securities:
Stock options and non-vested stock	217,000	164,000	222,000	166,000
Denominator for diluted earnings per share - adjusted weighted average shares and assumed conversion	35,917,105	33,398,648	35,358,332	32,972,262
Basic earnings per common share attributable to common shareholders	$ 0.88	$ 0.77	$ 2.35	$ 1.92	$ 2.68	$ 2.37	$ 1.88
Diluted earnings per common share attributable to common shareholders	$ 0.88	$ 0.77	$ 2.33	$ 1.91	$ 2.67	$ 2.36	$ 1.87

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities not included in the effect of dilutive securities	139,518	125,775	157,383	145,690
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities not included in the effect of dilutive securities	11,000	6,000	7,333	6,667

Shareholders' Equity - Reconcil

Shareholders' Equity - Reconciliation of Changes in Total Shareholders' Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Beginning balance			$ 975,869
Net proceeds from the issuance of common stock			175,521
Exercise of stock options			982
Earned portion of non-vested stock	$ 1,552	$ 1,129	4,743	$ 3,451
Stock option expense	46	37	163	186
Deferred compensation - directors			43
Adjustment to redemption value on noncontrolling redeemable Operating Partnership units			(924)
Net income attributable to common shareholders	31,504	25,589	82,487	62,838	$ 88,531	$ 74,126	$ 55,128
Change in fair value of derivatives	(4,537)	$ 2,464	(6,103)	$ (3,191)
Dividends			(82,742)
Ending balance	$ 1,150,039		$ 1,150,039		$ 975,869

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail)	Mar. 03, 2015USD ($)$ / sharesshares	Sep. 30, 2015USD ($)$ / sharesshares	Sep. 30, 2014USD ($)$ / sharesshares	Mar. 31, 2014USD ($)$ / sharesshares	Sep. 30, 2015USD ($)Facility$ / sharesshares	Sep. 30, 2014USD ($)$ / sharesshares	Dec. 31, 2014Facility	May. 12, 2014USD ($)
Stockholders Equity [Line Items]
Common stock shares issued under equity offering program | shares	1,380,000
Common stock, price per share, public offering | $ / shares	$ 90.40
Proceeds from issuance of common stock	$ 119,500,000
Common stock issued upon exercise of stock options | shares		1,900	3,962		16,900	12,962
Common stock value authorized under equity offering program								$ 225,000,000
Number of storage facilities acquired | Facility					26		33
Shares issued under dividend reinvestment plan | shares					105,876
Equity Program [Member]
Stockholders Equity [Line Items]
Common stock shares issued under equity offering program | shares		300,211	424,403		499,911	674,403
Proceeds from issuance of common stock		$ 28,500,000	$ 32,900,000		$ 46,500,000	$ 51,900,000
Common stock, value reserved for future issuance		$ 104,100,000			$ 104,100,000
Weighted average issue price of common stock | $ / shares		$ 96.13	$ 78.46		$ 94.29	$ 77.95
Number of storage facilities acquired | Facility					26
Equity Program [Member] | Hsbc Securities [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions			$ 400,000
Equity Program [Member] | Piper and Hsbc [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions						$ 700,000
Equity Program [Member] | Jefferies and Piper [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions					$ 600,000
Equity Program [Member] | Piper Jaffray & Co [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions		$ 400,000
Previous Equity Program [Member]
Stockholders Equity [Line Items]
Common stock shares issued under equity offering program | shares				359,102
Proceeds from issuance of common stock				$ 26,400,000
Weighted average issue price of common stock | $ / shares				$ 74.32
Previous Equity Program [Member] | SunTrust [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions				$ 300,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Sep. 30, 2015USD ($)Facility
Commitments and Contingencies Disclosure [Abstract]
Payment for self-storage facilities under contract | $	$ 66.7
Number of self-storage facilities under contract to be purchased	9

Reclassification - Additional I

Reclassification - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended			72 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2003
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative expenses	$ 9,367,000	$ 8,711,000	$ 28,459,000	$ 26,111,000	$ 35,222,000	$ 30,136,000	$ 28,465,000
Additional paid-in capital	1,337,656,000		1,337,656,000		1,156,225,000
Common stock value	$ 362,000		$ 362,000		341,000
Share Repurchase Program [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Repurchase of common shares								1,171,886
Additional paid-in capital					27,200,000
Common stock value					11,719
Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Advertising Expense		$ 1,330,000		$ 4,290,000
General and administrative expenses					(5,570,000)	$ (4,803,000)	$ (3,848,000)
Scenario, Previously Reported [Member] | Share Repurchase Program [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional paid-in capital					1,183,400,000
Common stock value					$ 353,000

Reclassification - Schedule of

Reclassification - Schedule of Consolidated Statements of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Rental income	$ 88,066	$ 79,092	$ 250,439	$ 223,438	$ 302,044	$ 253,384	$ 217,906
Other operating income	7,362	6,157	21,124	17,712	24,036	20,123	16,176
Total operating revenues	95,428	85,249	271,563	241,150	326,080	273,507	234,082
Expenses
Property operations and maintenance	20,954	19,243	61,001	55,720	75,333	66,119	59,011
Real estate taxes	9,247	8,312	27,311	24,433	32,097	26,496	22,076
General and administrative	9,367	8,711	28,459	26,111	35,222	30,136	28,465
Acquisition costs	1,046	1,210	2,415	5,926	7,359	3,129	4,328
Operating leases of storage facilities		1,997	683	5,991	7,987	1,331
Depreciation and amortization	14,671	13,357	43,437	37,780	51,749	45,233	40,542
Total operating expenses	55,285	52,830	163,306	155,961	209,747	172,444	154,422
Income from operations	40,143	32,419	108,257	85,189	116,333	101,063	79,660
Other income (expenses)
Interest expense	(9,419)	(9,116)	(27,796)	(25,331)	(34,578)	(32,000)	(33,166)
Interest income	1	1	4	31	40	40	4
Gain on sale of storage facilities		1,777	(7)	1,777	5,176
Gain on sale of real estate						421	687
Equity in income of joint ventures	936	662	2,436	1,553	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	31,661	25,743	82,894	63,219	89,057	74,595	55,641
Net income attributable to noncontrolling interest	(157)	(154)	(407)	(381)	(526)	(469)	(513)
Net income attributable to common shareholders	$ 31,504	$ 25,589	$ 82,487	$ 62,838	$ 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	$ 0.88	$ 0.77	$ 2.35	$ 1.92	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	$ 0.88	$ 0.77	$ 2.33	$ 1.91	$ 2.67	$ 2.36	$ 1.87

Reclassification - Schedule o64

Reclassification - Schedule of Consolidated Statements of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	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

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Oct. 26, 2015	Sep. 30, 2015	Oct. 02, 2015	Oct. 01, 2015
Subsequent Event [Line Items]
Dividend declared, date		Oct. 2, 2015
Dividend paid, date		Oct. 26, 2015
Dividend record, date		Oct. 16, 2015
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend per common share			$ 0.85
Dividend paid	$ 30.6
Subsequent Event [Member] | Florida Joint Venture [Member]
Subsequent Event [Line Items]
Interest in joint venture				85.00%
Development cost				$ 4