Changes in Shareholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018
Dividends declared per share	$ 0.05		$ 0.00		$ 0.10	$ 0.00
Net income (loss)	$ (15,260)	[1]	$ 37,141	[1]	$ 25,080	$ 72,361
Other Comprehensive Income (Loss), Net of Tax	(11,949)		2,242		(13,349)	(26,410)
Payments of Ordinary Dividends, Common Stock	(2,903)				(5,803)	0
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	88		(203)		(1,297)	(5,732)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	4,146		4,417		6,871	8,477
Stockholders' Equity Attributable to Parent	$ 650,917		$ 512,571		$ 650,917	$ 512,571	$ 676,795	$ 639,415	$ 468,974	$ 463,875
Common Stock [Member]
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures	49		89		245	795
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	$ 1		$ 1		$ 3	$ 8
Shares, Issued	58,067		57,436		58,067	57,436	58,018	57,822	57,347	56,641
Stockholders' Equity Attributable to Parent	$ 581		$ 574		$ 581	$ 574	$ 580	$ 578	$ 573	$ 566
Retained Earnings [Member]
Net income (loss)	(15,260)		37,141		25,080	72,361
Payments of Ordinary Dividends, Common Stock	(2,903)
Stockholders' Equity Attributable to Parent	223,472		75,731		223,472	75,731	241,635	204,195	38,590	3,370
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Other Comprehensive Income (Loss), Net of Tax	(11,949)		2,242		(13,349)	(26,410)
Additional Paid-in Capital [Member]
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures	87		(204)		(1,300)	(5,740)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	4,146		4,417		6,871	8,477
Stockholders' Equity Attributable to Parent	470,937		465,474		470,937	465,474	466,704	465,366	461,261	462,737
AOCI Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent	$ (44,073)		$ (29,208)		$ (44,073)	$ (29,208)	$ (32,124)	$ (30,724)	$ (31,450)	$ (2,798)

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