Fair Value Measurements - Narrative (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Unrealized gains on the investments after-tax	$ 605,000	$ 471,000
Money market funds
Cash and Cash Equivalents [Line Items]
Unrealized gains on the investments	0
Other mutual funds
Cash and Cash Equivalents [Line Items]
Unrealized gains on the investments	1,000,000	800,000
Fair Value, Measurements, Recurring
Cash and Cash Equivalents [Line Items]
Assets, Fair Value Disclosure	9,691,000	11,054,000
Fair Value, Measurements, Recurring | Money market funds
Cash and Cash Equivalents [Line Items]
Assets, Fair Value Disclosure	7,320,000	8,518,000
Fair Value, Measurements, Recurring | Other mutual funds
Cash and Cash Equivalents [Line Items]
Assets, Fair Value Disclosure	$ 2,371,000	$ 2,536,000