Results by Quarter (Unaudited) - Summary of Results by Quarter (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
RENTAL REVENUES	$ 209,275	$ 207,297	$ 199,422	$ 189,699	$ 195,376	$ 195,130	$ 194,907	$ 181,021	$ 805,693	$ 766,434	$ 737,724
Net income	$ 178,296	$ 178,597	$ 177,911	$ 142,722	$ 174,494	$ 176,260	$ 173,203	$ 134,918	$ 677,526	$ 658,875	$ 634,162
Net income per limited partnership unit	$ 20.17	$ 20.20	$ 20.13	$ 16.15	$ 19.75	$ 19.94	$ 19.59	$ 15.26	$ 76.65	$ 74.54	$ 71.74