Common Dividends Declared Per Share (Detail) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Common stock	$ 0.85	$ 0.85	$ 0.85
Common OP units	$ 0.868	$ 0.868	$ 0.868

Cash dividends declared or paid to each outstanding limited partnership unit during the reporting period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 5
-Subparagraph (SAB Topic 4.F)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

Name:	us-gaap_DistributionsPerLimitedPartnershipUnitOutstanding
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration