Commitments and Contingencies - Litigation Narrative (Details) $ in Thousands				1 Months Ended		6 Months Ended	12 Months Ended
	Feb. 05, 2019 USD ($)	Jun. 07, 2018 USD ($)	Sep. 08, 2016 plaintiff	Oct. 26, 2018 USD ($) lawsuit	Dec. 31, 2013 USD ($)	Jun. 30, 2019 USD ($) property lawsuit	Dec. 31, 2018 USD ($)	Jan. 20, 2015 lawsuit
Loss Contingencies [Line Items]
Litigation settlement payment						$ 245,400
Holdings as a percent of total pending shareholder actions						35.30%
SDNY Actions [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Number of claims | lawsuit								10
Opt-Out Actions [Member]
Loss Contingencies [Line Items]
Number of claims | lawsuit						13
Number of settled litigations | lawsuit				12
Twelve Opt-Out Actions [Member]
Loss Contingencies [Line Items]
Litigation settlement payment				$ 127,500
Holdings as a percent of total pending shareholder actions				18.00%
Vanguard Action [Member]
Loss Contingencies [Line Items]
Litigation settlement payment		$ 90,000
Holdings as a percent of total pending shareholder actions		13.00%
Series of Individual Agreements [Member]
Loss Contingencies [Line Items]
Litigation settlement payment	$ 27,900
Putative Class Action [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Stipulation of settlement, maximum attorney fees					$ 625
Audit Committee Investigation [Member] | SDNY Actions [Member]
Loss Contingencies [Line Items]
Number of individuals in civil complaint | plaintiff			2
Insurance Recoveries, Net of Litigation and Non-Routine Costs [Member]
Loss Contingencies [Line Items]
Litigation settlement payment						$ 12,200	$ 15,700
Acquisition, 2019 [Member] | Build-to-suit Development Project [Member]
Loss Contingencies [Line Items]
Number of real estate properties acquired | property						1
Remaining investment						$ 11,900