Debt - Senior Unsecured Term Loan Facility (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Unsecured revolving credit facility		$ 0	$ 35,192,000
Revolving credit facility [Member] | Term Loan [Member]
Debt Instrument [Line Items]
Unsecured revolving credit facility	$ 265,000,000.0	$ 265,000,000	$ 265,000,000
Pay Rate		2.1485%
Prepayment premium, period one	2.00%
Prepayment premium, period two	1.00%
Revolving credit facility [Member] | Term Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		1.60%
Minimum [Member] | Revolving credit facility [Member] | Term Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.40%
Minimum [Member] | Revolving credit facility [Member] | Term Loan [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	0.40%
Maximum [Member] | Revolving credit facility [Member] | Term Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.35%
Maximum [Member] | Revolving credit facility [Member] | Term Loan [Member] | Base Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.35%