Debt (Details)			1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 24, 2015 USD ($)	Jun. 25, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Oct. 31, 2014 USD ($)	Aug. 31, 2014 USD ($)	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) item	Jun. 29, 2015 USD ($) item
Credit Facility and Term Loan
Proceeds from line of credit									$ 25,000,000
Transaction costs							$ 849,000		849,000		$ 227,000
Interest paid									32,526,000	$ 36,557,000
Loss on extinguishment of debt							$ (18,581,000)	$ (1,180,000)	$ (22,478,000)	(1,180,000)
2015 Credit Facility | LIBOR
Credit Facility and Term Loan
LIBOR floor (as a percent)							0.00%		0.00%
2015 Credit Facility | Minimum
Credit Facility and Term Loan
Commitment fees on unused revolving credit commitment (as a percent)									0.25%
2015 Credit Facility | Minimum | LIBOR
Credit Facility and Term Loan
Variable applicable rate (as a percent)									1.50%
2015 Credit Facility | Minimum | Base Rate
Credit Facility and Term Loan
Variable applicable rate (as a percent)									0.50%
2015 Credit Facility | Maximum
Credit Facility and Term Loan
Commitment fees on unused revolving credit commitment (as a percent)									0.40%
2015 Credit Facility | Maximum | LIBOR
Credit Facility and Term Loan
Variable applicable rate (as a percent)									2.25%
2015 Credit Facility | Maximum | Base Rate
Credit Facility and Term Loan
Variable applicable rate (as a percent)									1.25%
2011 Credit Facility
Credit Facility and Term Loan
Debt issuance costs				$ 2,700,000
Revolving credit facility | 2015 Credit Facility
Credit Facility and Term Loan
Maximum borrowing capacity		$ 5,000,000					$ 5,000,000		$ 5,000,000
Proceeds from line of credit	$ 25,000,000
Principal of debt							100,000,000		$ 100,000,000
Term of debt instrument									5 years
Transaction costs							897,000		$ 897,000
Commitment fee expense							15,000		15,000
Revolving credit facility | 2011 Credit Facility
Credit Facility and Term Loan
Outstanding borrowings											0
Interest expense								0	$ 0	0
Commitment fees on unused revolving credit commitment (as a percent)									0.50%
Commitment fee expense								38,000	$ 89,000	113,000
Senior secured term loan facility
Credit Facility and Term Loan
Principal value of debt redeemed (as a percent)			100.00%
Extinguishment of amount owed			$ 285,800,000
Redemption price (as a percent)			105.25%
Face value of notes repurchased			$ 271,500,000
Debt issuance costs			4,300,000
Loss on extinguishment of debt			$ 18,600,000
Senior secured term loan facility | 2015 Credit Facility
Credit Facility and Term Loan
Principal payment on debt		80,000,000
Amount borrowed	$ 245,000,000
Principal of debt							325,000,000		$ 325,000,000
Term of debt instrument									5 years
Additional principal payments required as a percentage of excess cash flow									50.00%
Additional principal payments required as a percentage of net cash proceeds of dispositions or casualty events, if not invested within one year									100.00%
Period of time within which proceeds must be reinvested									1 year
Additional principal payments required as a percentage of net cash proceeds from issuance of debt or Preferred Stock									100.00%
Transaction costs							2,800,000		$ 2,800,000
Outstanding balance under the Term Loan, net of unamortized transaction costs									322,200,000
Interest paid							422,000		422,000
Interest expense							$ 1,500,000		$ 1,500,000
Effective interest rate (as a percent)							2.33%		2.33%
Weighted average nominal interest rate (as a percent)							2.09%		2.09%
Senior secured term loan facility | 2015 Credit Facility | Consolidated leverage ratio, equal to or less than 3.00 to 1.00 but greater than 2.00 to 1.00
Credit Facility and Term Loan
Additional principal payments required as a percentage of excess cash flow									25.00%
Senior secured term loan facility | 2015 Credit Facility | Consolidated leverage ratio, equal to or less than 3.00 to 1.00 but greater than 2.00 to 1.00 | Minimum
Credit Facility and Term Loan
Consolidated leverage ratio									2.00
Senior secured term loan facility | 2015 Credit Facility | Consolidated leverage ratio, equal to or less than 3.00 to 1.00 but greater than 2.00 to 1.00 | Maximum
Credit Facility and Term Loan
Consolidated leverage ratio									3.00
Senior secured term loan facility | 2015 Credit Facility | Consolidated leverage ratio, equal to or less than 2.00 to 1.00
Credit Facility and Term Loan
Additional principal payments required as a percentage of excess cash flow									0.00%
Senior secured term loan facility | 2015 Credit Facility | Consolidated leverage ratio, equal to or less than 2.00 to 1.00 | Maximum
Credit Facility and Term Loan
Consolidated leverage ratio									2.00
Senior secured term loan facility | 2011 Credit Facility
Credit Facility and Term Loan
Principal payment on debt				19,600,000				11,500,000	$ 119,600,000	36,500,000
Transaction costs											4,300,000
Outstanding balance under the Term Loan, net of unamortized transaction costs											$ 115,400,000
Interest expense								$ 1,600,000	2,700,000	$ 5,100,000
Effective interest rate (as a percent)								5.10%		5.03%
Weighted average nominal interest rate (as a percent)								4.05%		4.05%
Purchase price of notes repurchased				99,600,000
Debt issuance costs				1,200,000
Loss on extinguishment of debt				$ 3,900,000
Letter of Credit | 2015 Credit Facility
Credit Facility and Term Loan
Maximum borrowing capacity		$ 15,000,000					$ 15,000,000		$ 15,000,000
Number of letters of credit outstanding | item												1
Amount of letter of credit outstanding												$ 909,000
Letter of Credit | 2011 Credit Facility
Credit Facility and Term Loan
Number of letters of credit outstanding | item							1		1		1
Amount of letter of credit outstanding											$ 202,000
Notes
Credit Facility and Term Loan
Transaction costs											4,800,000
Outstanding balance under the Term Loan, net of unamortized transaction costs											$ 266,700,000
Interest expense							$ 2,000,000	$ 8,000,000	$ 16,600,000	$ 24,100,000
Effective interest rate (as a percent)							11.00%	11.00%	11.00%	11.00%
Purchase price of notes repurchased					$ 22,100,000	$ 9,500,000
Face value of notes repurchased					20,000,000	8,500,000
Debt issuance costs					368,000	160,000
Loss on extinguishment of debt					$ (2,500,000)	$ (1,200,000)