Fair Value Measurement: (Details) (USD $) In Thousands | 3 Months Ended | 9 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011
Fair Value, Measurements, Recurring [Member]
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Dec. 31, 2010
Fair Value, Measurements, Recurring [Member]
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Sep. 30, 2011
Fair Value, Measurements, Recurring [Member]
Quoted prices in active markets for identical assets (level 1)
Certificates of Deposit [Member] | Dec. 31, 2010
Fair Value, Measurements, Recurring [Member]
Quoted prices in active markets for identical assets (level 1)
Certificates of Deposit [Member] | Sep. 30, 2011
Fair Value, Measurements, Recurring [Member]
Signifcant other observable inputs (level 2)
Nontaxable Municipal Notes [Member] | Dec. 31, 2010
Fair Value, Measurements, Recurring [Member]
Signifcant other observable inputs (level 2)
Nontaxable Municipal Notes [Member] | Sep. 30, 2011
Fair Value, Measurements, Recurring [Member]
Significant unobservable inputs (level 3) | Dec. 31, 2010
Fair Value, Measurements, Recurring [Member]
Significant unobservable inputs (level 3) | |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||||||
| Available for sale securities | $ 52,153 | $ 14,507 | $ 5,079 | $ 2,820 | $ 47,074 | $ 11,687 | $ 0 | $ 0 | ||||
| Level 3 investments | 0 | 0 | ||||||||||
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ||||||||||||
| Investments, Beginning Balance | 750 | 900 | ||||||||||
| Transfers into Level 3 | 0 | 0 | ||||||||||
| Sales | (750) | (900) | ||||||||||
| Unrealized holdig loss, included in other comprehensive income | 0 | 0 | ||||||||||
| Investments, Ending Balance | $ 0 | $ 0 | ||||||||||