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		$ 23,144,000	$ 35,204,000		$ (1,859,000)	$ (33,595,000)
Balance, beginning of year at Dec. 31, 2018		23,144,000	35,204,000		(1,859,000)	(33,595,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		145,000
Compensation amortization under share-based plans and other changes		83,000
Shareholders' equity	$ 25,321,000	23,372,000	36,135,000		206,000	(34,392,000)
Net income (loss)	1,353,000		1,353,000
Dividends			(421,000)
Other			(1,000)
Other comprehensive income	2,065,000				2,065,000
Treasury stock acquired — share repurchase authorization						(750,000)
Net shares acquired related to employee share-based compensation plans						(47,000)
Balance, end of period at Jun. 30, 2019	25,321,000	23,372,000	36,135,000		206,000	(34,392,000)
Balance, beginning of year (in shares) at Dec. 31, 2018							263.6
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)							(5.5)
Net shares issued under employee share-based compensation plans (in shares)							2.2
Balance, end of period (in shares) at Jun. 30, 2019							260.3
Shareholders' Equity [Roll Forward]
Shareholders' equity		23,243,000	35,795,000		(682,000)	(34,016,000)
Balance, beginning of year at Mar. 31, 2019		23,243,000	35,795,000		(682,000)	(34,016,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		91,000
Compensation amortization under share-based plans and other changes		38,000
Shareholders' equity	25,321,000	23,372,000	36,135,000		206,000	(34,392,000)
Net income (loss)	557,000		557,000
Dividends			(217,000)
Other			0
Other comprehensive income	888,000				888,000
Treasury stock acquired — share repurchase authorization						(375,000)
Net shares acquired related to employee share-based compensation plans						(1,000)
Balance, end of period at Jun. 30, 2019	25,321,000	23,372,000	36,135,000		206,000	(34,392,000)
Balance, beginning of year (in shares) at Mar. 31, 2019							261.9
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)							(2.6)
Net shares issued under employee share-based compensation plans (in shares)							1.0
Balance, end of period (in shares) at Jun. 30, 2019							260.3
Shareholders' Equity [Roll Forward]
Shareholders' equity	25,321,000	23,372,000	36,135,000		206,000	(34,392,000)
Shareholders' equity	25,943,000	23,469,000	36,977,000		640,000	(35,143,000)
Shareholders' equity | Accounting Standards Update 2016-13 [Member]				$ (43,000)
Balance, beginning of year at Dec. 31, 2019	25,943,000	23,469,000	36,977,000		640,000	(35,143,000)
Balance, beginning of year (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2019				(43,000)
Shareholders' Equity [Roll Forward]
Employee share-based compensation		56,000
Compensation amortization under share-based plans and other changes		81,000
Shareholders' equity	25,943,000	23,606,000	37,069,000		640,000	(35,614,000)
Shareholders' equity | Accounting Standards Update 2016-13 [Member]				$ (43,000)
Net income (loss)	560,000		560,000
Dividends			(428,000)
Other			3,000
Other comprehensive income	1,242,000				1,242,000
Treasury stock acquired — share repurchase authorization	(425,000)					(425,000)
Net shares acquired related to employee share-based compensation plans	(46,000)					(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						255.5
Common shares outstanding
Treasury stock acquired - share repurchase authorization (in shares)	(3.5)						(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						253.2
Shareholders' Equity [Roll Forward]
Shareholders' equity		23,542,000	37,325,000		(49,000)	(35,614,000)
Balance, beginning of year 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
Shareholders' equity	$ 26,943,000	23,606,000	37,069,000		1,882,000	(35,614,000)
Net income (loss)	(40,000)		(40,000)
Dividends			(218,000)
Other			2,000
Other comprehensive income	1,931,000				1,931,000
Treasury stock acquired — share repurchase authorization						0
Net shares acquired related to employee share-based compensation plans	(33)					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 authorization (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						253.2
Shareholders' Equity [Roll Forward]
Shareholders' equity	$ 26,943,000	$ 23,606,000	$ 37,069,000		$ 1,882,000	$ (35,614,000)