CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cumulative dividends declared per common share	$ 0.41		$ 0.41	$ 1.41	$ 0.41	$ 0.41	$ 0.41	$ 0.82	$ 1.23
NET INCOME	$ 36,548	$ 23,541	$ 16,882	$ 33,655	$ 39,577	$ 39,700	$ 33,346	$ 76,971	$ 112,623
Other comprehensive income, net of income tax	(2,601)	(1,520)	46,823	(7,264)	4,610	16,016	12,790
Accrual of dividends on common stock	(15,037)	(15)	(14,583)	(50,521)	(14,130)	(14,354)	(14,490)
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered	2,516	1,397	1,534	2,029	1,672	575	950
Total shareholders’ equity	$ 1,646,529	1,625,103	$ 1,601,700	$ 1,594,034	$ 1,530,935	$ 1,521,055	$ 1,511,191	$ 1,646,529	$ 1,530,935	$ 1,478,595
Cumulative dividends declared per common share	$ 0.41		$ 0.41	$ 1.41	$ 0.41	$ 0.41	$ 0.41	$ 0.82	$ 1.23
Retained Earnings [Member]
NET INCOME	$ 36,548	23,541	$ 16,882	$ 33,655	$ 39,577	$ 39,700	$ 33,346
Accrual of dividends on common stock	(15,037)	(15)	(14,583)	(50,521)	(14,130)	(14,354)	(14,490)
Total shareholders’ equity	222,959	201,448	177,922	186,838	203,704	178,257	152,911	$ 222,959	$ 203,704	134,055
Accumulated Other Comprehensive Income (Loss) [Member]
Other comprehensive income, net of income tax	(2,601)	(1,520)	46,823	(7,264)	4,610	16,016	12,790
Total shareholders’ equity	$ 75,958	$ 78,559	$ 80,079	$ 33,256	$ 40,520	$ 35,910	$ 19,894	$ 75,958	$ 40,520	$ 7,104
Common Stock [Member]
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered (in shares)	669	55,440	(24,337)	(132)	(286)	20,897	(30,026)
Shares, Outstanding	35,158,568	35,157,899	35,102,459	35,751,576	34,173,357	34,573,643	35,152,746	35,158,568	34,173,357	35,182,772
Common Stock and Paid in Capital [Member]
Amortization of stock-based compensation related to restricted stock grants, net of shares surrendered	$ 2,516	$ 1,397	$ 1,534	$ 2,029	$ 1,672	$ 575	$ 950
Total shareholders’ equity	$ 1,347,612	$ 1,345,096	$ 1,343,699	$ 1,373,940	$ 1,286,711	$ 1,306,888	$ 1,338,386	$ 1,347,612	$ 1,286,711	$ 1,337,436