Subsequent Events - Narrative (Details) - Subsequent event $ in Millions		1 Months Ended
	Jul. 15, 2017 USD ($)	Jul. 31, 2017 USD ($) ft²
Held-for-sale | 1500 Market Street
Subsequent Event [Line Items]
Square footage (in sqft) | ft²		1,759,193
Gross sales price		$ 328.0
6.65% Senior Unsecured Notes Due 2018
Subsequent Event [Line Items]
Debt redeemed at par	$ 250.0
Debt instrument, interest rate	6.65%