Related Party and Affiliated Real Estate Joint Venture Transactions - Management Fee Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Management fee revenues and other income	$ 39,842	$ 34,161	$ 28,215
VRS Self Storage LLC Joint Venture [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	1,053	1,398	1,326
PREXR {Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	20	0	0
SPI [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	2,160	2,075	1,999
PRISA [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	6,117	5,809	5,466
ESW II [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	482	452	410
ESSM [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	162	152	132
WCOT [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	1,819	1,799	1,680
PRISA II [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	3,469	4,703	4,635
ESW [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	555	515	480
ESNPS [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	620	584	550
HSRE-ESP IA, LLC (HSRE) [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	0	0	1,201
Other [Member]
Related Party Transaction [Line Items]
Management fee revenues and other income	$ 23,385	$ 16,674	$ 10,336