Fair Value of Financial Instruments (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets:
Assets, fair value	$ 20,955	$ 46,011
Quotes Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Assets, fair value	8,169	20,005
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets, fair value	11,786	25,006
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Assets, fair value	1,000	1,000
Money market funds (cash equivalents) [Member]
Assets:
Assets, fair value	8,169
Money market funds (cash equivalents) [Member] | Quotes Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Assets, fair value	8,169
Corporate notes and bonds [Member]
Assets:
Assets, fair value	7,182
Corporate notes and bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets, fair value	7,182
U.S. government and agency securities [Member]
Assets:
Assets, fair value	3,805
U.S. government and agency securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets, fair value	3,805
Preferred securities [Member]
Assets:
Assets, fair value	1,000	1,000
Preferred securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Assets, fair value	1,000	1,000
Certificates of deposit [Member]
Assets:
Assets, fair value		25,006
Certificates of deposit [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets, fair value		25,006
Commercial paper [Member]
Assets:
Assets, fair value	799
Commercial paper [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Assets, fair value	799
Cash equivalents [Member]
Assets:
Assets, fair value		20,005
Cash equivalents [Member] | Quotes Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Assets, fair value		$ 20,005