Shareholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Facility	Feb. 27, 2013
Stockholders Equity [Line Items]
Common stock value authorized under equity offering program		$ 175
Common stock shares issued under equity offering program	359,102
Weighted average issue price of common stock	$ 74.32
Proceeds from issuance of common stock	26.4
Expenses related to equity program	0.1
Acquired storage facilities	7
Common stock, value reserved for future issuance	38.8
Shares issued under dividend reinvestment plan	47,583
SunTrust [Member]
Stockholders Equity [Line Items]
Offering related costs and commissions	$ 0.3