Long-term Debt - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Carrying value	$ 389,077,000		$ 389,077,000				$ 391,057,000
Amortization of debt issuance costs	30,000	$ 30,000	61,000	$ 61,000
Amended Facility
Debt Instrument [Line Items]
Carrying value	389,100,000		389,100,000				391,000,000
Unrestricted cash and cash equivalents limit for the secured leverage ratio	$ 40,000,000		$ 40,000,000
Secured leverage ratio	4.00		4.00
Amended Facility | Scenario, forecast
Debt Instrument [Line Items]
Secured leverage ratio					3.75	4.00
Amended Facility | Term loan
Debt Instrument [Line Items]
Carrying value	$ 389,100,000		$ 389,100,000				391,000,000
Fair value	$ 394,900,000		$ 394,900,000				$ 386,200,000
Effective interest rate	3.84%		3.84%				4.03%
Quarterly principal payment			$ 1,000,000
End of term payment	$ 373,200,000		373,200,000
Amended Facility | Revolving credit facility
Debt Instrument [Line Items]
Outstanding borrowings	$ 0		$ 0				$ 0