CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Cumulative dividends declared per common share	$ 0.41	$ 0.41	$ 0.41		$ 0	$ 0.41	$ 0.82	$ 0.41
New credit standard (ASC 326) - impact in year of adoption						$ (11,215)
NET INCOME	$ 54,382	$ 46,855	$ 38,957	$ 36,548	$ 23,541	16,882	$ 101,237	$ 40,423
Other comprehensive income, net of income tax	25,285	(56,103)	(6,889)	(2,601)	(1,520)	46,823
Accrual of dividends on common stock	(14,459)	(14,589)	(14,600)	(15,037)	(15)	(14,583)
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered	(259)	1,714	2,267	2,516	1,397	1,534
Repurchase of common stock	(14,555)	(25,324)				(31,775)
Total shareholders’ equity	$ 1,669,211	$ 1,618,817	$ 1,666,264	$ 1,646,529	$ 1,625,103	$ 1,601,700	$ 1,669,211	$ 1,625,103	$ 1,594,034
Cumulative dividends declared per common share	$ 0.41	$ 0.41	$ 0.41		$ 0	$ 0.41	$ 0.82	$ 0.41
Common Stock [Member]
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered (in shares)	65,545	76,143	632	669	55,440	(24,337)
Stock Repurchased and Retired During Period, Shares	(250,000)	(500,000)				(624,780)
Shares, Outstanding	34,550,888	34,735,343	35,159,200	35,158,568	35,157,899	35,102,459	34,550,888	35,157,899	35,751,576
Common Stock and Paid in Capital [Member]
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered	$ (259)	$ 1,714	$ 2,267	$ 2,516	$ 1,397	$ 1,534
Repurchase of common stock	(14,555)	(25,324)				(31,775)
Total shareholders’ equity	1,311,455	1,326,269	1,349,879	1,347,612	1,345,096	1,343,699	$ 1,311,455	$ 1,345,096	$ 1,373,940
Retained Earnings [Member]
New credit standard (ASC 326) - impact in year of adoption						(11,215)
NET INCOME	54,382	46,855	38,957	36,548	23,541	16,882
Accrual of dividends on common stock	(14,459)	(14,589)	(14,600)	(15,037)	(15)	(14,583)
Total shareholders’ equity	319,505	279,582	247,316	222,959	201,448	177,922	319,505	201,448	186,838
Accumulated Other Comprehensive Income (Loss) [Member]
Other comprehensive income, net of income tax	25,285	(56,103)	(6,889)	(2,601)	(1,520)	46,823
Total shareholders’ equity	$ 38,251	$ 12,966	$ 69,069	$ 75,958	$ 78,559	$ 80,079	$ 38,251	$ 78,559	$ 33,256