Income Taxes Deferred Income Tax Assets and Liabilities (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Net current deferred tax assets	$ 18,800,000
Deferred tax assets:
Accruals and reserves not currently deductible	10,331,000	10,945,000
Deferred income	9,354,000	11,831,000
Tax net operating loss and credit carryforwards	6,712,000	8,596,000
Non-qualified stock compensation	5,049,000	3,017,000
Capitalized research and development	95,000	73,000
Unrealized impairment of auction rate securities	208,000	371,000
Gross deferred tax assets	31,749,000	34,833,000
Valuation allowance	(7,625,000)	0
Total deferred tax assets	24,124,000	34,833,000
Deferred tax liabilities:
Depreciation	(5,351,000)	(5,147,000)
State income taxes	0	(88,000)
Total deferred tax liability	(5,351,000)	(5,235,000)
Net deferred tax assets (current and non-current)	18,773,000	29,598,000
State and Local Jurisdiction [Member]
Deferred tax liabilities:
State research and development credit carryfrowards	18,100,000
Pre-ownership change carryforwards	$ 2,300,000