Condensed Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Shares	Preferred Shares	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2017		29,696,682
Balance at Dec. 31, 2017	$ 694,699	$ 6	$ 0	$ 636,149	$ 48,198	$ 10,346
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	52,198				52,198
Other comprehensive income (loss)	(29,494)					(29,494)
Dividends	(27,189)				(27,189)
Exercise of stock options (in shares)		210,134
Exercise of stock options	3,175			3,175
Vesting of RSUs (in shares)		43,304
Vesting of RSUs	(777)			(777)
Compensation expense under share incentive plans	4,796			4,796
Balance (in shares) at Sep. 30, 2018		29,950,120
Balance at Sep. 30, 2018	697,408	$ 6	0	643,343	77,178	(23,119)
Balance (in shares) at Jun. 30, 2018		29,917,821
Balance at Jun. 30, 2018	689,243	$ 6	0	641,290	66,677	(18,730)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	19,581				19,581
Other comprehensive income (loss)	(4,389)					(4,389)
Dividends	(9,080)				(9,080)
Exercise of stock options (in shares)		32,299
Exercise of stock options	372			372
Compensation expense under share incentive plans	1,681			1,681
Balance (in shares) at Sep. 30, 2018		29,950,120
Balance at Sep. 30, 2018	$ 697,408	$ 6	0	643,343	77,178	(23,119)
Balance (in shares) at Dec. 31, 2018	29,988,460	29,988,460
Balance at Dec. 31, 2018	$ 709,241	$ 6	0	645,310	79,753	(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	30,401,270
Balance at Sep. 30, 2019	$ 768,969	$ 6	0	655,998	78,344	34,621
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	30,401,270
Balance at Sep. 30, 2019	$ 768,969	$ 6	$ 0	$ 655,998	$ 78,344	$ 34,621