Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of assets and liabilities measured at fair value on recurring basis
Interest rate swaps	$ 553	$ 510
Level 1 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Interest rate swaps
Level 2 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Interest rate swaps	553	510
Level 3 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Interest rate swaps
Money market mutual funds [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	10,158	8,818
Money market mutual funds [Member] | Level 1 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	10,158	8,818
Money market mutual funds [Member] | Level 2 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Money market mutual funds [Member] | Level 3 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Government agency bonds [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	4,008	9,015
Government agency bonds [Member] | Level 1 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	3,686	9,015
Government agency bonds [Member] | Level 2 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Government agency bonds [Member] | Level 3 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Corporate notes [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	3,686	3,019
Corporate notes [Member] | Level 1 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	4,008	3,019
Corporate notes [Member] | Level 2 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Corporate notes [Member] | Level 3 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
United States treasuries [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	3,005
United States treasuries [Member] | Level 1 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	3,005
United States treasuries [Member] | Level 2 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
United States treasuries [Member] | Level 3 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Certificates of deposit [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	1,925	2,701
Certificates of deposit [Member] | Level 1 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value	1,925	2,701
Certificates of deposit [Member] | Level 2 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value
Certificates of deposit [Member] | Level 3 [Member]
Schedule of assets and liabilities measured at fair value on recurring basis
Assets measured at fair value