Long-term Debt - Narrative (Details) - USD ($)			3 Months Ended			6 Months Ended
	Apr. 15, 2014	Apr. 12, 2011	Jun. 30, 2015	Jun. 30, 2014	Apr. 15, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Senior secured notes			$ 150,000,000			$ 150,000,000		$ 150,000,000
Senior Secured Notes [Member]
Debt Instrument [Line Items]
Private placement date		Apr. 12, 2011
Issuance of private placement, principal amount		$ 200,000,000.0
Interest rate		8.75%
Term of payments of interest on notes		semi-annually
Total amount of debt to be retired	$ 50,000,000				$ 50,000,000
Percentage of debt to be retired from the total debt	25.00%				25.00%
Aggregate face amount of debt redeemed	$ 45,000,000				$ 45,000,000
Redemption price as a percentage of face amount					106.563%
Senior secured notes	150,000,000				$ 150,000,000
Annual interest cost reduction due to retirement of debt	3,900,000
Interest expense on note			$ 3,300,000	$ 3,400,000		$ 6,600,000	$ 7,700,000
November Two Thousand Eleven Senior Notes [Member]
Debt Instrument [Line Items]
Total amount of debt to be retired	$ 5,000,000				$ 5,000,000