Fair Value Measurements (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value Measurements [Abstract]
Transfers from Level 1 to Level 2		$ 0	$ 0
Transfers from Level 2 to Level 1		0	0
Recurring Basis [Member]
Fair Value Measurements [Abstract]
Cash equivalents	[1]	69,107
Total		112,330
Recurring Basis [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities	[2]	40,225
Recurring Basis [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities	[2]	2,998
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Fair Value Measurements [Abstract]
Cash equivalents		69,107	$ 7,100
Total		69,107
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0
Recurring Basis [Member] | Quoted Prices in Active Markets (Level 1) [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		0
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Measurements [Abstract]
Cash equivalents		0
Total		43,223
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		40,225
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Municipal Debt Securities [Member]
Fair Value Measurements [Abstract]
Available-for-sale securities		2,998
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements [Abstract]
Total		$ 0

[1] Included in cash and cash equivalents on our condensed consolidated balance sheets.

[2] Included in short-term investments on our condensed consolidated balance sheets.