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
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	17,868					17,868
Other comprehensive income (loss)	50,449							50,449
Dividends	(27,557)					(27,557)
Exercise of stock options (in shares)			336,533
Exercise of stock options	6,799				6,799
Vesting of RSUs (in shares)			76,277
Vesting of RSUs	(1,374)				(1,374)
Compensation expense under share incentive plans	5,263				5,263
Balance (in shares) at Sep. 30, 2019			30,401,270
Balance at Sep. 30, 2019	$ 768,969		$ 6	0	655,998	78,344		34,621
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
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]
Net (loss) income	(25,167)					(25,167)
Other comprehensive income (loss)	9,457							9,457
Dividends	(9,218)					(9,218)
Exercise of stock options (in shares)			70,595
Exercise of stock options	1,068				1,068
Compensation expense under share incentive plans	1,779				1,779
Balance (in shares) at Sep. 30, 2019			30,401,270
Balance at Sep. 30, 2019	$ 768,969		$ 6	0	655,998	78,344		34,621
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	25,082					25,082
Other comprehensive income (loss)	47,433							47,433
Dividends	$ (27,815)					(27,815)
Exercise of stock options (in shares)	79,615		79,615
Exercise of stock options	$ 2,529				2,529
Vesting of RSUs (in shares)			106,147
Vesting of RSUs	(2,186)				(2,186)
Compensation expense under share incentive plans	$ 5,874				5,874
Balance (in shares) at Sep. 30, 2020	30,610,153		30,610,153
Balance at Sep. 30, 2020	$ 821,406		$ 6	0	664,092	78,761		78,547
Balance (in shares) at Jun. 30, 2020			30,553,178
Balance at Jun. 30, 2020	795,711		$ 6	0	660,427	61,770		73,508
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	26,283					26,283
Other comprehensive income (loss)	5,039							5,039
Dividends	(9,292)					(9,292)
Exercise of stock options (in shares)			50,474
Exercise of stock options	1,691				1,691
Vesting of RSUs (in shares)			6,501
Vesting of RSUs	(123)				(123)
Compensation expense under share incentive plans	$ 2,097				2,097
Balance (in shares) at Sep. 30, 2020	30,610,153		30,610,153
Balance at Sep. 30, 2020	$ 821,406		$ 6	$ 0	$ 664,092	$ 78,761		$ 78,547