UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings
Increase (Decrease) in Stockholders' Equity
Cumulative effect of change in accounting principle	$ (1,564)				$ (1,564)
Balance beginning of period at Dec. 31, 2017	1,188,202	$ 565	$ 686,962	$ (172,407)	673,082
Balance beginning of period (in shares) at Dec. 31, 2017		56,501
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(12,631)				(12,631)
Other comprehensive (loss) income	(16,746)			(16,746)
Stock-based compensation	3,077		3,077
Issuance of restricted shares, net of shares remitted and tax withholdings	(548)	$ 0	(548)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		24
Repurchases of common stock	(14,264)	$ (3)	(14,261)
Repurchases of common stock (in shares)		(280)
Balance ending of period at Mar. 31, 2018	1,145,526	$ 562	675,230	(189,153)	658,887
Balance ending of period (in shares) at Mar. 31, 2018		56,245
Balance beginning of period at Dec. 31, 2017	1,188,202	$ 565	686,962	(172,407)	673,082
Balance beginning of period (in shares) at Dec. 31, 2017		56,501
Increase (Decrease) in Stockholders' Equity
Net income (loss)	49,205
Other comprehensive (loss) income	(13,098)
Repurchases of common stock	$ (33,600)
Repurchases of common stock (in shares)	(600)
Balance ending of period at Sep. 30, 2018	$ 1,197,324	$ 560	661,546	(185,505)	720,723
Balance ending of period (in shares) at Sep. 30, 2018		55,998
Balance beginning of period at Mar. 31, 2018	1,145,526	$ 562	675,230	(189,153)	658,887
Balance beginning of period (in shares) at Mar. 31, 2018		56,245
Increase (Decrease) in Stockholders' Equity
Net income (loss)	30,747				30,747
Other comprehensive (loss) income	(4,942)			(4,942)
Stock-based compensation	3,562		3,562
Issuance of restricted shares, net of shares remitted and tax withholdings	(1,627)	$ 1	(1,628)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		94
Repurchases of common stock	(12,218)	$ (2)	(12,216)
Repurchases of common stock (in shares)		(252)
Balance ending of period at Jun. 30, 2018	1,161,048	$ 561	664,948	(194,095)	689,634
Balance ending of period (in shares) at Jun. 30, 2018		56,087
Increase (Decrease) in Stockholders' Equity
Net income (loss)	31,089				31,089
Other comprehensive (loss) income	8,590			8,590
Stock-based compensation	4,087		4,087
Issuance of restricted shares, net of shares remitted and tax withholdings	(391)	$ 0	(391)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		15
Repurchases of common stock	$ (7,099)	$ (1)	(7,098)
Repurchases of common stock (in shares)	(100)	(104)
Balance ending of period at Sep. 30, 2018	$ 1,197,324	$ 560	661,546	(185,505)	720,723
Balance ending of period (in shares) at Sep. 30, 2018		55,998
Balance beginning of period at Dec. 31, 2018	1,169,756	$ 558	655,415	(223,371)	737,154
Balance beginning of period (in shares) at Dec. 31, 2018		55,847
Increase (Decrease) in Stockholders' Equity
Net income (loss)	976				976
Other comprehensive (loss) income	4,024			4,024
Stock-based compensation	5,809		5,809
Issuance of restricted shares, net of shares remitted and tax withholdings	(2,276)	$ 1	(2,277)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		78
Repurchases of common stock	(6,324)	$ (1)	(6,323)
Repurchases of common stock (in shares)		(97)
Balance ending of period at Mar. 31, 2019	1,171,965	$ 558	652,624	(219,347)	738,130
Balance ending of period (in shares) at Mar. 31, 2019		55,828
Balance beginning of period at Dec. 31, 2018	1,169,756	$ 558	655,415	(223,371)	737,154
Balance beginning of period (in shares) at Dec. 31, 2018		55,847
Increase (Decrease) in Stockholders' Equity
Net income (loss)	73,589
Other comprehensive (loss) income	(319)
Repurchases of common stock	$ (16,400)
Repurchases of common stock (in shares)	(200)
Balance ending of period at Sep. 30, 2019	$ 1,235,795	$ 558	648,184	(223,690)	810,743
Balance ending of period (in shares) at Sep. 30, 2019		55,808
Balance beginning of period at Mar. 31, 2019	1,171,965	$ 558	652,624	(219,347)	738,130
Balance beginning of period (in shares) at Mar. 31, 2019		55,828
Increase (Decrease) in Stockholders' Equity
Net income (loss)	36,244				36,244
Other comprehensive (loss) income	5,076			5,076
Stock-based compensation	3,834		3,834
Issuance of restricted shares, net of shares remitted and tax withholdings	(2,704)	$ 1	(2,705)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		105
Repurchases of common stock	(4,948)		(4,948)
Repurchases of common stock (in shares)		(74)
Balance ending of period at Jun. 30, 2019	1,209,467	$ 559	648,805	(214,271)	774,374
Balance ending of period (in shares) at Jun. 30, 2019		55,859
Increase (Decrease) in Stockholders' Equity
Net income (loss)	36,369				36,369
Other comprehensive (loss) income	(9,419)			(9,419)
Stock-based compensation	5,021		5,021
Issuance of restricted shares, net of shares remitted and tax withholdings	(525)		(525)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		17
Repurchases of common stock	$ (5,118)	$ (1)	(5,117)
Repurchases of common stock (in shares)	(100)	(68)
Balance ending of period at Sep. 30, 2019	$ 1,235,795	$ 558	$ 648,184	$ (223,690)	$ 810,743
Balance ending of period (in shares) at Sep. 30, 2019		55,808