Line of Credit Payable (Details) - USD ($)	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Revolving credit facility borrowing capacity	$ 650,000,000
Revolving credit facility weighted average outstanding balance	$ 80,750,000
Revolving credit facility weighted average interest rate	1.40%
Option to increase facility size	$ 1,000,000,000
Line of credit payable	184,200,000	$ 0
Line of credit facility available for future borrowings	465,800,000
Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, undrawn letters of credit	$ 230,000
Line of Credit | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.925%