Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands, shares in Millions	Total	Common stock [Member]	Retained earnings [Member]	Retained earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated other comprehensive income (loss), net of tax [Member]	Treasury stock, at cost [Member]	Common shares outstanding [Member]
Shareholders' Equity [Roll Forward]
Shareholders' equity		$ 23,469,000	$ 36,977,000	$ (43,000)	$ 640,000	$ (35,143,000)
Balance, beginning of period at Dec. 31, 2019		23,469,000	36,977,000	$ (43,000)	640,000	(35,143,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		56,000
Compensation amortization under share-based plans and other changes		81,000
Net income (loss)	$ 560,000		560,000
Dividends			(428,000)
Other			3,000
Other comprehensive income (loss)	1,242,000				1,242,000
Treasury stock acquired — share repurchase authorizations						(425,000)
Net shares acquired related to employee share-based compensation plans						(46,000)
Balance, end of period at Jun. 30, 2020	26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Balance, beginning of year (in shares) at Dec. 31, 2019							255.5
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)							(3.5)
Net shares issued under employee share-based compensation plans (in shares)							1.2
Balance, end of period (in shares) at Jun. 30, 2020							253.2
Shareholders' Equity [Roll Forward]
Shareholders' equity		23,542,000	37,325,000		(49,000)	(35,614,000)
Balance, beginning of period at Mar. 31, 2020		23,542,000	37,325,000		(49,000)	(35,614,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		29,000
Compensation amortization under share-based plans and other changes		35,000
Net income (loss)	(40,000)		(40,000)
Dividends			(218,000)
Other			2,000
Other comprehensive income (loss)	1,931,000				1,931,000
Treasury stock acquired — share repurchase authorizations						0
Net shares acquired related to employee share-based compensation plans						0
Balance, end of period at Jun. 30, 2020	26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Balance, beginning of year (in shares) at Mar. 31, 2020							252.8
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)							0.0
Net shares issued under employee share-based compensation plans (in shares)							0.4
Balance, end of period (in shares) at Jun. 30, 2020							253.2
Shareholders' Equity [Roll Forward]
Shareholders' equity	26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Shareholders' equity	29,201,000	23,743,000	38,771,000		2,502,000	(35,815,000)
Balance, beginning of period at Dec. 31, 2020	29,201,000	23,743,000	38,771,000		2,502,000	(35,815,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		169,000
Compensation amortization under share-based plans and other changes		90,000
Net income (loss)	1,667,000		1,667,000
Dividends			(440,000)
Other			0
Other comprehensive income (loss)	(733,000)				(733,000)
Treasury stock acquired — share repurchase authorizations	(756,000)					(756,000)
Net shares acquired related to employee share-based compensation plans	(42,000)					(42,000)
Balance, end of period at Jun. 30, 2021	$ 29,156,000	24,002,000	39,998,000		1,769,000	(36,613,000)
Balance, beginning of year (in shares) at Dec. 31, 2020	252.4						252.4
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)	(5.0)						(5.0)
Net shares issued under employee share-based compensation plans (in shares)							2.1
Balance, end of period (in shares) at Jun. 30, 2021	249.5						249.5
Shareholders' Equity [Roll Forward]
Shareholders' equity		23,905,000	39,285,000		1,291,000	(36,212,000)
Balance, beginning of period at Mar. 31, 2021		23,905,000	39,285,000		1,291,000	(36,212,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		61,000
Compensation amortization under share-based plans and other changes		36,000
Net income (loss)	$ 934,000		934,000
Dividends			(224,000)
Other			3,000
Other comprehensive income (loss)	478,000				478,000
Treasury stock acquired — share repurchase authorizations	(400,000)					(400,000)
Net shares acquired related to employee share-based compensation plans	(144)					(1,000)
Balance, end of period at Jun. 30, 2021	$ 29,156,000	24,002,000	39,998,000		1,769,000	(36,613,000)
Balance, beginning of year (in shares) at Mar. 31, 2021							251.5
Common shares outstanding
Treasury stock acquired - share repurchase authorizations (in shares)	(2.6)						(2.6)
Net shares issued under employee share-based compensation plans (in shares)							0.6
Balance, end of period (in shares) at Jun. 30, 2021	249.5						249.5
Shareholders' Equity [Roll Forward]
Shareholders' equity	$ 29,156,000	$ 24,002,000	$ 39,998,000		$ 1,769,000	$ (36,613,000)