Fair Value Measurements - Financial Instruments Carried and Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities, restricted, long-term	$ 0	$ 336
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities, restricted, long-term		336
Total assets at fair value		336
Stock appreciation rights, liability-classified equity award		742
Total liabilities at fair value		742
Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities, restricted, long-term		0
Total assets at fair value		0
Stock appreciation rights, liability-classified equity award		0
Total liabilities at fair value		0
Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities, restricted, long-term		336
Total assets at fair value		336
Stock appreciation rights, liability-classified equity award		742
Total liabilities at fair value		742
Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities, restricted, long-term		0
Total assets at fair value		0
Stock appreciation rights, liability-classified equity award		0
Total liabilities at fair value		$ 0