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)
Net income	10,992					10,992
Other comprehensive income (loss), net of tax	21,612				22,144	(532)
Issuance of common stock (in shares)		297,000
Issuance of common stock	3,110	$ 3		3,107
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
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, 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)
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)		(2,869,000)