Mortgage Notes Payable, Credit Facilities and Senior Notes - Carrying Value of the Company’s Senior Notes (Details) - USD ($)	Dec. 31, 2016	Jul. 26, 2016	Dec. 31, 2015	Sep. 29, 2015	Dec. 03, 2014	Dec. 09, 2013
Debt Instrument [Line Items]
Long-term debt	$ 70,683,000		$ 61,683,000
Net unamortized deferred financing costs	(417,000)		(449,000)
Long-term Debt	299,191,000		298,802,000
Credit facility	95,654,000		132,028,000
Term Loan Agreement
Debt Instrument [Line Items]
Long-term debt	300,000,000		300,000,000
Principal amount				$ 300,000,000.0
Net unamortized deferred financing costs	(809,000)		(1,198,000)
Long-term Debt	299,191,000		298,802,000
Senior Notes Due 2026
Debt Instrument [Line Items]
Principal amount	200,000,000	$ 200,000,000.0	0
Net unamortized deferred financing costs	(273,000)		0
Senior Notes	199,727,000		0
Senior Notes Due 2024
Debt Instrument [Line Items]
Long-term debt	250,000,000		250,000,000
Principal amount					$ 250,000,000.0
Unamortized debt discount	(2,891,000)		(3,191,000)
Net unamortized deferred financing costs	(1,755,000)		(1,976,000)
Senior Notes	245,354,000		244,833,000
Senior Notes Due 2023
Debt Instrument [Line Items]
Long-term debt	250,000,000		250,000,000
Principal amount						$ 250,000,000.0
Unamortized debt discount	(3,119,000)		(3,482,000)
Net unamortized deferred financing costs	(1,830,000)		(2,092,000)
Senior Notes	245,051,000		244,426,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility	98,000,000		135,500,000
Net unamortized deferred financing costs	(2,346,000)		(3,472,000)
Credit facility	$ 95,654,000		$ 132,028,000