Organization and Principles of Consolidation (Details)	3 Months Ended
	Mar. 31, 2015
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Operations commenced date	Dec. 31, 1993
Wholly Owned Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of real estate properties	201
Unconsolidated Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of real estate properties	120
Parent Company [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage of outstanding common partnership units	99.80%