Limited Partners' Non-Controlling Interests in the Parent Company (Textual) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Aggregate amount related to non-controlling interests classified within equity	$ 15.2	$ 15.2
Settlement value of non controlling interest in operating partnership	$ 25.0	$ 26.9

Carrying amount of the equity interests owned by noncontrolling partners in an operating partnership included in the entity's consolidated financial statements.

No definition available.

Name:	us-gaap_MinorityInterestInOperatingPartnerships
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant