CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Total
Balance at Dec. 31, 2015	$ 1,359,144	$ (825)	$ (940,027)	$ 418,292
Balance (in shares) at Dec. 31, 2015	298,634
Increase (Decrease) in Shareholders' Equity
Stock-based compensation	$ 353			353
Return of capital distribution (note 8)	(1,489)			(1,489)
Share repurchase	$ (582)			(582)
Share repurchase (in shares)	(558)
Other-than-temporary impairment on marketable equity securities (note 2)		285		285
Unrealized gain (loss) on available-for-sale securities, net of taxes (note 2)		(124)		(124)
Net income			12,985	12,985
Balance at Mar. 31, 2016	$ 1,357,426	(664)	(927,042)	429,720
Balance (in shares) at Mar. 31, 2016	298,076
Balance at Dec. 31, 2016	$ 1,360,345	1,666	(918,972)	443,039
Balance (in shares) at Dec. 31, 2016	299,570
Increase (Decrease) in Shareholders' Equity
Stock-based compensation	$ 330			330
Return of capital distribution (note 8)	(1,498)			(1,498)
Exercise of stock options (note 8)	$ 47			47
Exercise of stock options (note 8) (in shares)	20
Unrealized gain (loss) on available-for-sale securities, net of taxes (note 2)		3,875		3,875
Net income			(3,018)	(3,018)
Balance at Mar. 31, 2017	$ 1,359,224	$ 5,541	$ (921,990)	$ 442,775
Balance (in shares) at Mar. 31, 2017	299,590