Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Voting Common Stock [Member] Common Stock [Member]	Nonvoting Common Stock [Member] Common Stock [Member]	Paid-In Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Balance at Dec. 31, 2015	$ 216	$ 95	$ 1,020,129	$ (9,592)	$ (873,660)	$ (28,698)	$ 108,490
Balance, shares at Dec. 31, 2015	21,582	9,506		154
Net income (loss)					47,200
Other comprehensive income (loss)						14,862
Comprehensive income (loss)							62,062
Tax benefit associated with stock-based compensation			(141)				(141)
Balance at Dec. 31, 2016	$ 216	$ 95	1,019,988	$ (9,592)	(826,460)	(13,836)	170,411
Balance, shares at Dec. 31, 2016	21,582	9,506		154
Net income (loss)					71,359		71,359
Other comprehensive income (loss)						(3,038)	(3,038)
Comprehensive income (loss)							68,321
Cumulative effect adjustment attributable to previously unrecognized excess tax benefits on stock-based compensation					4,741		4,741
Balance at Mar. 31, 2017	$ 216	$ 95	$ 1,019,988	$ (9,592)	$ (750,360)	$ (16,874)	$ 243,473
Balance, shares at Mar. 31, 2017	21,582	9,506		154