Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Shares	Preferred Shares	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2018			29,988,460
Balance at Dec. 31, 2018	$ 709,241	$ 8,280	$ 6	$ 0	$ 645,310	$ 79,753	$ 8,280	$ (15,828)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	43,035					43,035
Other comprehensive income (loss)	40,992							40,992
Dividends	(18,339)					(18,339)
Exercise of stock options (in shares)			265,938
Exercise of stock options	5,731				5,731
Vesting of RSUs (in shares)			76,277
Vesting of RSUs	(1,374)				(1,374)
Compensation expense under share incentive plans	3,484				3,484
Balance (in shares) at Jun. 30, 2019			30,330,675
Balance at Jun. 30, 2019	$ 791,050		$ 6	0	653,151	112,729		25,164
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Balance (in shares) at Mar. 31, 2019			30,162,045
Balance at Mar. 31, 2019	$ 754,297		$ 6	0	648,242	101,617		4,432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	20,307					20,307
Other comprehensive income (loss)	20,732							20,732
Dividends	(9,195)					(9,195)
Exercise of stock options (in shares)			166,963
Exercise of stock options	3,099				3,099
Vesting of RSUs (in shares)			1,667
Vesting of RSUs	0				0
Compensation expense under share incentive plans	1,810				1,810
Balance (in shares) at Jun. 30, 2019			30,330,675
Balance at Jun. 30, 2019	$ 791,050		$ 6	0	653,151	112,729		25,164
Balance (in shares) at Dec. 31, 2019	30,424,391		30,424,391
Balance at Dec. 31, 2019	$ 778,581		$ 6	0	657,875	89,586		31,114
Balance (ASU 2019-05) at Dec. 31, 2019		(7,827)					(7,827)
Balance (ASU 2016-13) at Dec. 31, 2019		(265)					(265)
Balance (ASU 2019-05) at Jan. 01, 2020							(7,800)
Balance (ASU 2016-13) at Jan. 01, 2020							(265)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List] | ASU 2019-05	us-gaap:AccountingStandardsUpdate201905Member
Accounting Standards Update [Extensible List] | ASU 2016-13	us-gaap:AccountingStandardsUpdate201613Member
Balance (in shares) at Dec. 31, 2019	30,424,391		30,424,391
Balance at Dec. 31, 2019	$ 778,581		$ 6	0	657,875	89,586		31,114
Balance (ASU 2019-05) at Dec. 31, 2019		(7,827)					(7,827)
Balance (ASU 2016-13) at Dec. 31, 2019		$ (265)					$ (265)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(1,201)					(1,201)
Other comprehensive income (loss)	42,394							42,394
Dividends	$ (18,523)					(18,523)
Exercise of stock options (in shares)	29,141		29,141
Exercise of stock options	$ 838				838
Vesting of RSUs (in shares)			99,646
Vesting of RSUs	(2,063)				(2,063)
Compensation expense under share incentive plans	$ 3,777				3,777
Balance (in shares) at Jun. 30, 2020	30,553,178		30,553,178
Balance at Jun. 30, 2020	$ 795,711		$ 6	0	660,427	61,770		73,508
Balance (in shares) at Mar. 31, 2020			30,520,428
Balance at Mar. 31, 2020	720,317		$ 6	0	657,704	35,412		27,195
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	35,614					35,614
Other comprehensive income (loss)	46,313							46,313
Dividends	(9,256)					(9,256)
Exercise of stock options (in shares)			29,141
Exercise of stock options	838				838
Vesting of RSUs (in shares)			3,609
Vesting of RSUs	(25)				(25)
Compensation expense under share incentive plans	$ 1,910				1,910
Balance (in shares) at Jun. 30, 2020	30,553,178		30,553,178
Balance at Jun. 30, 2020	$ 795,711		$ 6	$ 0	$ 660,427	$ 61,770		$ 73,508