Fair Value Measurements (Details) (Fair value measured on a recurring basis [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value	$ 19,460	$ 27,895
Municipal Bonds [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value	13,820	22,892
Certificates of Deposit [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value	5,640	5,003
Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value	19,460	27,895
Level 1 [Member] | Municipal Bonds [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value	13,820	22,892
Level 1 [Member] | Certificates of Deposit [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value	5,640	5,003
Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value
Level 2 [Member] | Municipal Bonds [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value
Level 2 [Member] | Certificates of Deposit [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value
Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value
Level 3 [Member] | Municipal Bonds [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value
Level 3 [Member] | Certificates of Deposit [Member]
Assets and liabilities measured at fair value on a recurring basis, by input level
Total assets at fair value