Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value Measurements
Amount of transfers of financial assets between Level 1 and Level 2 measures	$ 0
Available-for-sale equity securities
Assets:
Short term investments:	75,366	96,942
Recurring
Assets:
Total short-term investments	75,386
Recurring | Available-for-sale equity securities
Assets:
Short term investments:	75,366
Recurring | Mortgage-CMO debt securities
Assets:
Short term investments:	20
Recurring | Level 1
Assets:
Total short-term investments	74,504
Recurring | Level 1 | Available-for-sale equity securities
Assets:
Short term investments:	74,504
Recurring | Level 2
Assets:
Total short-term investments	882
Recurring | Level 2 | Available-for-sale equity securities
Assets:
Short term investments:	862
Recurring | Level 2 | Mortgage-CMO debt securities
Assets:
Short term investments:	$ 20