Acquisitions - 2015 Acquisitions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
333 Dexter [Member]
Business Acquisition [Line Items]
Business acquisition, date of acquisition agreement	Feb. 13, 2015
Payments to acquire land	$ 49.5
Accrued liabilities and acquisition costs	$ 2.4
100 Hooper [Member]
Business Acquisition [Line Items]
Business acquisition, date of acquisition agreement	Jul. 07, 2015
Payments to acquire land	$ 78.0
Accrued liabilities and acquisition costs	4.1
2015 Total Acquisitions [Member]
Business Acquisition [Line Items]
Payments to acquire land	$ 127.5