Financial Instruments and Fair Value Measurements (Carrying Amounts and Fair Value) (Details) (USD $) | 3 Months Ended | 12 Months Ended | | |
In Thousands, unless otherwise specified | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2013 | Dec. 31, 2012 |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | $39,800 | $44,644 | ' | ' |
Cash | 11,248 | 14,092 | ' | ' |
Money market funds | 15,175 | 16,431 | ' | ' |
Cash and Cash Equivalents, at Carrying Value | 26,423 | 33,462 | 25,916 | 44,114 |
Available-for-sale Securities, Amortized Cost Basis | 106,888 | 102,644 | ' | ' |
Short-term investments | 48,833 | 46,325 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Gain, Before Tax | 67 | 38 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Loss, Before Tax | -104 | -72 | ' | ' |
Long-term investments | 58,018 | 56,285 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss | -104 | -72 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 39,800 | 44,644 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss | 104 | 72 | ' | ' |
Available-for-sale Securities | 106,851 | 102,610 | ' | ' |
Municipal Bonds [Member] | ' | ' | ' | ' |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | ' | 552 | ' | ' |
Available-for-sale Securities, Amortized Cost Basis | 3,108 | 3,827 | ' | ' |
Short-term investments | 3,115 | 3,830 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Gain, Before Tax | 7 | 5 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Loss, Before Tax | 0 | -2 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss | ' | -2 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | ' | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss | ' | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | ' | 552 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss | ' | 2 | ' | ' |
US Government Agencies Debt Securities [Member] | ' | ' | ' | ' |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 16,272 | 20,614 | ' | ' |
Available-for-sale Securities, Amortized Cost Basis | 38,934 | 45,672 | ' | ' |
Short-term investments | 38,920 | 45,658 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Gain, Before Tax | 18 | 12 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Loss, Before Tax | -32 | -26 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss | -32 | -26 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 16,272 | 20,614 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss | 32 | 26 | ' | ' |
US Treasury Securities [Member] | ' | ' | ' | ' |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 7,780 | 4,361 | ' | ' |
Available-for-sale Securities, Amortized Cost Basis | 20,662 | 11,430 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Gain, Before Tax | 6 | 3 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Loss, Before Tax | -46 | -5 | ' | ' |
Long-term investments | 20,622 | 11,428 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss | -46 | -5 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 7,780 | 4,361 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss | 46 | 5 | ' | ' |
Certificates of Deposit [Member] | ' | ' | ' | ' |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 6,412 | 12,714 | ' | ' |
Available-for-sale Securities, Amortized Cost Basis | 15,000 | 14,945 | ' | ' |
Short-term investments | 14,998 | 14,920 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Gain, Before Tax | 11 | 1 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Loss, Before Tax | -13 | -26 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss | -13 | -26 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 6,412 | 12,714 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss | 13 | 26 | ' | ' |
Corporate Note Securities [Member] | ' | ' | ' | ' |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 9,336 | 6,403 | ' | ' |
Available-for-sale Securities, Amortized Cost Basis | 29,184 | 26,770 | ' | ' |
Short-term investments | 29,196 | 26,774 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Gain, Before Tax | 25 | 17 | ' | ' |
Available-For-Sale Securities, Accumulated Gross Unrealized Loss, Before Tax | -13 | -13 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss | -13 | -13 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss | 0 | 0 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value | 9,336 | 6,403 | ' | ' |
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss | 13 | 13 | ' | ' |
US Government Agencies Debt Securities [Member] | ' | ' | ' | ' |
Schedule of Available-for-sale Securities [Line Items] | ' | ' | ' | ' |
Available-for-sale Securities, Amortized Cost Basis | ' | 2,939 | ' | ' |
Short-term investments | ' | $2,939 | ' | ' |