Consolidated Condensed Schedule Of Investments Consolidated Condensed Schedule of Investments (Cash Equivalents) - Cash Equivalents [Member] - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Schedule of Investments [Line Items]
Money Market Funds, at Carrying Value		$ 90,000	[1]	$ 160,000	[2]
Money Market Funds, at Cost		$ 90,000	[1]	$ 160,000	[2]
Money market funds as a percentage of stockholders' equity		13.96%	[1],[3]	21.65%	[2],[4]
BlackRock Liquidity Funds FedFund Portfolio, Institutional Class Shares [Member]
Schedule of Investments [Line Items]
Money Market Funds, at Carrying Value	[1]	$ 50,000
Investment Owned, Balance, Shares	[1]	50,000
Rate	[1]	0.42%
BlackRock Liquidity Funds TempFund Portfolio [Member]
Schedule of Investments [Line Items]
Money Market Funds, at Carrying Value	[2]			$ 100,000
Investment Owned, Balance, Shares	[2]			100,000
Rate	[2]			0.04%
JPMorgan Prime Money Market Fund [Member]
Schedule of Investments [Line Items]
Money Market Funds, at Carrying Value	[2]			$ 50,000
Investment Owned, Balance, Shares	[2]			50,000
Rate	[2]			0.01%
Various Money Market Funds [Member]
Schedule of Investments [Line Items]
Money Market Funds, at Carrying Value		$ 40,000	[1]	$ 10,000	[2]
Investment Owned, Balance, Shares		40,000	[1]	10,000	[2]
Rate	[2]			0.00%
Various Money Market Funds [Member] | Minimum [Member]
Schedule of Investments [Line Items]
Rate	[1]	0.44%
Various Money Market Funds [Member] | Maximum [Member]
Schedule of Investments [Line Items]
Rate	[1]	0.45%

[1] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.

[2] See Note 2 and Note 3 in Notes to Consolidated Financial Statements.

[3] Classification percentages are based on Total Equity.

[4] Classification percentages are based on Total Equity.