Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets Measured On Recurring Basis [Line Items]
Liabilities, fair value disclosure, non-recurring	$ 0	$ 0
Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	3,793	2,770
U.S. Treasury Securities (Cash Equivalents) [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets		1,002
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	3,793	2,770
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury Securities (Cash Equivalents) [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets		1,002
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Securities (Cash Equivalents) [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets		0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets	$ 0	0
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury Securities (Cash Equivalents) [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Fair value assets		$ 0