Fair Value Accounting - Recurring Basis (Details) - USD ($) $ in Thousands | Jun. 30, 2016 | Dec. 31, 2015 |
Marketable Securities, Current [Abstract] | | |
Fair value, current | $ 21,183 | $ 17,500 |
Marketable Securities, Noncurrent [Abstract] | | |
Fair value, non-current | 593 | 1,397 |
Equity securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 14,804 | |
Corporate notes and bonds | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 4,614 | 15,489 |
Marketable Securities, Noncurrent [Abstract] | | |
Fair value, non-current | 593 | 1,397 |
Mortgage securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 1,765 | 2,011 |
Fair Value, Measurements, Recurring [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 31,520 | 21,723 |
Fair Value, Measurements, Recurring [Member] | Equity securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 14,803 | |
Fair Value, Measurements, Recurring [Member] | Corporate notes and bonds | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 4,614 | 15,489 |
Marketable Securities, Noncurrent [Abstract] | | |
Fair value, non-current | 593 | 1,397 |
Fair Value, Measurements, Recurring [Member] | Mortgage securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 1,766 | 2,011 |
Fair Value, Measurements, Recurring [Member] | Cash | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 1,844 | 1,674 |
Fair Value, Measurements, Recurring [Member] | Money market funds | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 7,900 | 1,152 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 25,140 | 2,826 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 14,803 | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate notes and bonds | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 0 | 0 |
Marketable Securities, Noncurrent [Abstract] | | |
Fair value, non-current | 593 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 1,844 | 1,674 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money market funds | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 7,900 | 1,152 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 4,614 | 16,886 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 0 | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate notes and bonds | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 4,614 | 15,489 |
Marketable Securities, Noncurrent [Abstract] | | |
Fair value, non-current | 0 | 1,397 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money market funds | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 1,766 | 2,011 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 0 | |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate notes and bonds | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 0 | 0 |
Marketable Securities, Noncurrent [Abstract] | | |
Fair value, non-current | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage securities | | |
Marketable Securities, Current [Abstract] | | |
Fair value, current | 1,766 | 2,011 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money market funds | | |
Cash and cash equivalents: | | |
Cash and Cash Equivalents, Fair Value Disclosure | $ 0 | $ 0 |