Income Taxes - The components of the net deferred income tax asset (liability) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Depreciation and amortization	$ 11,655	$ 19,378
Deferred revenue	1,932	1,044
Net operating loss carryforwards	73,246	75,873
Alternative minimum tax credit carryforward	2,194	2,124
Research and development tax credit carryforward	1,236	1,078
Accrued expenses and other	8,889	8,572
Total deferred tax assets	99,152	108,069
Deferred tax liabilities:
Depreciation and amortization	8,914	2,791
Intangible assets	(4,784)	(6,595)
Deferred expenses and other	(521)	(577)
Total deferred tax liabilities	(14,219)	(9,963)
Valuation allowance:
Beginning balance	(100,492)	(108,066)
Decrease during the period	100,492	7,574
Total valuation allowance	0	(100,492)
Net deferred tax asset (liability)	84,933	(2,386)
Deferred income tax liability	(7,578)	(2,470)
Deferred income tax asset	$ 92,511	$ 84