Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance (in shares) at Dec. 31, 2017		61,476
Beginning Balance at Dec. 31, 2017	$ 1,015,479	$ 122,952	$ 226,937	$ 690,674	$ (25,084)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(437,012)			(437,012)
Other comprehensive loss	(20,528)				(20,528)
Dividends declared ($0.86 per share for 2018, $1.03 per share for 2017, $1.02 per share for 2016)	(52,992)			(52,992)
Share-based compensation expense, exercises and other (in shares)		818
Share-based compensation expense, exercises and other	$ 13,472	$ 1,636	11,836
Ending Balance (in shares) at Dec. 31, 2018	61,476	62,294
Ending Balance at Dec. 31, 2018	$ 518,419	$ 124,588	238,773	200,670	(45,612)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(62,371)			(62,371)
Other comprehensive loss	(7,095)				(7,095)
Dividends declared ($0.86 per share for 2018, $1.03 per share for 2017, $1.02 per share for 2016)	(525)			(525)
Share-based compensation expense, exercises and other (in shares)		549
Share-based compensation expense, exercises and other	$ 13,726	$ 1,098	12,628
Ending Balance (in shares) at Dec. 31, 2019	62,294	62,843
Ending Balance at Dec. 31, 2019	$ 462,154	$ 125,686	$ 251,401	$ 137,774	$ (52,707)