Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 251,741	$ 255,139
Income taxes receivable	10,851	11,105
Other current assets	4,350	3,099
Total current assets	266,942	269,343
Income taxes receivable, non-current	1,550	1,550
Investments in affiliates	39,306	53,430
Deferred tax assets	55,145	50,016
Other assets	366	372
Total assets	363,309	374,711
Current liabilities:
Accrued employment costs	1,283	2,573
Other current liabilities	1,718	1,279
Total current liabilities	3,001	3,852
Pension and other postretirement liabilities	18,429	18,786
Other liabilities	61,950	61,475
Total liabilities	83,380	84,113
Commitments and contingencies
Shareholders' Equity:
Preferred stock, 0.01 par value; 10,000,000 shares authorized, no shares issued and outstanding
Common Stock:
Paid-in capital	1,019,988	1,019,988
Accumulated deficit	(700,644)	(682,831)
Accumulated other comprehensive loss	(30,134)	(37,278)
Total shareholders' equity	279,929	290,598
Total liabilities and shareholders' equity	363,309	374,711
Voting Common Stock [Member]
Common Stock:
Common stock, 0.01 par value	216	216
Treasury stock (at cost), 154,494 shares of voting common stock	(9,592)	(9,592)
Non-voting Common Stock [Member]
Common Stock:
Common stock, 0.01 par value	$ 95	$ 95