CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common shares par value [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Accumulated other comprehensive loss [Member]
Balance at Dec. 31, 2013	$ 550,457	$ 50,344	$ 22,596	$ 510,941	$ (33,424)
Balance, shares at Dec. 31, 2013	50,344
Net income	$ 199,794			199,794
Cash dividends	(57,603)			(57,603)
Common shares issued	$ 15,301	720	14,581
Common shares issued, shares	720
Tax impact of share-based awards	$ 4,398		4,398
Common shares repurchased	$ (60,119)	(1,133)	(35,585)	(23,401)
Common shares repurchased, shares	(1,133)
Other common shares retired	$ (10,649)	(189)	(10,064)	(396)
Other common shares retired, shares	(189)
Fair value of share-based compensation	$ 8,832		8,832
Other comprehensive (loss) income	(2,914)				(2,914)
Balance at Dec. 31, 2014	$ 647,497	49,742	4,758	629,335	(36,338)
Balance, shares at Dec. 31, 2014	49,742
Net income	$ 218,629			218,629
Cash dividends	(59,755)			(59,755)
Common shares issued	$ 7,987	324	7,663
Common shares issued, shares	324
Tax impact of share-based awards	$ 2,021		2,021
Common shares repurchased	$ (59,952)	(996)	(22,000)	(36,956)
Common shares repurchased, shares	(996)
Other common shares retired	$ (3,225)	(51)	(3,174)
Other common shares retired, shares	(51)
Fair value of share-based compensation	$ 10,732		10,732
Other comprehensive (loss) income	(18,865)				(18,865)
Balance at Dec. 31, 2015	$ 745,069	49,019	0	751,253	(55,203)
Balance, shares at Dec. 31, 2015	49,019
Net income	$ 229,382			229,382
Cash dividends	(58,720)			(58,720)
Common shares issued	$ 17,785	641	17,144
Common shares issued, shares	641
Common shares repurchased	$ (55,224)	(901)	(15,203)	(39,120)
Common shares repurchased, shares	(901)
Other common shares retired	$ (13,640)	(213)	(13,427)
Other common shares retired, shares	(213)
Fair value of share-based compensation	$ 11,486		11,486
Other comprehensive (loss) income	4,832				4,832
Balance at Dec. 31, 2016	$ 880,970	$ 48,546	$ 0	$ 882,795	$ (50,371)
Balance, shares at Dec. 31, 2016	48,546