CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDER'S EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance Beginning of Period, Shares (in shares) at Dec. 31, 2017		81,306,000
Balance, Beginning of Period at Dec. 31, 2017	$ 962,306	$ 813	$ (121,644)	$ 821,758	$ (23,807)	$ 285,186
Balance, Beginning of Period, Treasury Stock, Shares (in shares) at Dec. 31, 2017			(2,927,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	10,992					10,992
Other comprehensive income (loss), net of tax	21,612				22,144	(532)
Issuance of common stock through employee stock purchase plan	553			553
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes (in shares)		108,000	37,000
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes	(6,732)	$ 1	$ 910	(7,643)
Share-based compensation	4,745			4,745
Issuance of common stock (in shares)		297,000
Issuance of common stock	3,110	$ 3		3,107
Balance End of Period, Shares (in shares) at Mar. 31, 2018		81,711,000
Balance, End of Period at Mar. 31, 2018	998,440	$ 817	$ (120,734)	822,520	(1,663)	297,500
Balance, End of Period, Treasury Stock, Shares (in shares) at Mar. 31, 2018			(2,890,000)
Balance Beginning of Period, Shares (in shares) at Dec. 31, 2017		81,306,000
Balance, Beginning of Period at Dec. 31, 2017	962,306	$ 813	$ (121,644)	821,758	(23,807)	285,186
Balance, Beginning of Period, Treasury Stock, Shares (in shares) at Dec. 31, 2017			(2,927,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,368
Balance End of Period, Shares (in shares) at Jun. 30, 2018		87,772,000
Balance, End of Period at Jun. 30, 2018	1,341,905	$ 877	$ (120,732)	1,177,125	(25,306)	309,941
Balance, End of Period, Treasury Stock, Shares (in shares) at Jun. 30, 2018			(2,890,000)
Balance Beginning of Period, Shares (in shares) at Mar. 31, 2018		81,711,000
Balance, Beginning of Period at Mar. 31, 2018	998,440	$ 817	$ (120,734)	822,520	(1,663)	297,500
Balance, Beginning of Period, Treasury Stock, Shares (in shares) at Mar. 31, 2018			(2,890,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,376					11,376
Other comprehensive income (loss), net of tax	(22,578)				(23,643)	1,065
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes (in shares)		16,000
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes	(467)		$ 2	(469)
Share-based compensation	5,471			5,471
Issuance of common stock (in shares)		39,000
Issuance of common stock	65			65
Exercise of warrants (in shares)		6,038,000
Equity offering	349,598	$ 60		349,538
Balance End of Period, Shares (in shares) at Jun. 30, 2018		87,772,000
Balance, End of Period at Jun. 30, 2018	1,341,905	$ 877	$ (120,732)	1,177,125	(25,306)	309,941
Balance, End of Period, Treasury Stock, Shares (in shares) at Jun. 30, 2018			(2,890,000)
Balance Beginning of Period, Shares (in shares) at Dec. 31, 2018		88,044,000
Balance, Beginning of Period at Dec. 31, 2018	$ 1,375,796	$ 880	$ (120,615)	1,192,601	(45,443)	348,373
Balance, Beginning of Period, Treasury Stock, Shares (in shares) at Dec. 31, 2018	(2,881,000)		(2,881,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 32,756					32,756
Other comprehensive income (loss), net of tax	(11,236)				(11,236)
Issuance of common stock through employee stock purchase plan (in shares)		17,000
Issuance of common stock through employee stock purchase plan	716			716
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes (in shares)		243,000	12,000
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes	(5,121)	$ 2	$ 506	(5,629)
Share-based compensation	4,119			4,119
Balance End of Period, Shares (in shares) at Mar. 31, 2019		88,304,000
Balance, End of Period at Mar. 31, 2019	1,397,030	$ 882	$ (120,109)	1,191,807	(56,679)	381,129
Balance, End of Period, Treasury Stock, Shares (in shares) at Mar. 31, 2019			(2,869,000)
Balance Beginning of Period, Shares (in shares) at Dec. 31, 2018		88,044,000
Balance, Beginning of Period at Dec. 31, 2018	$ 1,375,796	$ 880	$ (120,615)	1,192,601	(45,443)	348,373
Balance, Beginning of Period, Treasury Stock, Shares (in shares) at Dec. 31, 2018	(2,881,000)		(2,881,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 62,492
Other comprehensive income (loss), net of tax	(23,257)
Balance End of Period, Shares (in shares) at Jun. 30, 2019		88,351,000
Balance, End of Period at Jun. 30, 2019	$ 1,420,951	$ 883	$ (120,107)	1,198,010	(68,700)	410,865
Balance, End of Period, Treasury Stock, Shares (in shares) at Jun. 30, 2019	(2,869,000)		(2,869,000)
Balance Beginning of Period, Shares (in shares) at Mar. 31, 2019		88,304,000
Balance, Beginning of Period at Mar. 31, 2019	$ 1,397,030	$ 882	$ (120,109)	1,191,807	(56,679)	381,129
Balance, Beginning of Period, Treasury Stock, Shares (in shares) at Mar. 31, 2019			(2,869,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,736					29,736
Other comprehensive income (loss), net of tax	(12,021)				(12,021)
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes (in shares)		47,000
Issuance of common stock for vesting of share based awards, net of shares withheld for taxes	408	$ 1	$ 2	405
Share-based compensation	5,798			5,798
Balance End of Period, Shares (in shares) at Jun. 30, 2019		88,351,000
Balance, End of Period at Jun. 30, 2019	$ 1,420,951	$ 883	$ (120,107)	$ 1,198,010	$ (68,700)	$ 410,865
Balance, End of Period, Treasury Stock, Shares (in shares) at Jun. 30, 2019	(2,869,000)		(2,869,000)