Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Straight-line rent adjustments	$ 51.9	$ 46.8

Amount of the adjustment to rental revenues to measure escalating leasing revenues on a straight line basis.

No definition available.

Name:	us-gaap_StraightLineRentAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration