Condensed Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands		Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2018		$ 2,536,568		$ 0	$ 26,559	$ 1,084,391	$ 2,337,252		$ (911,634)
Beginning balance (in shares) at Dec. 31, 2018					53,116,485
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		132,777					120,531		12,246
Common stock dividends declared and paid		(58,056)					(58,056)
Common stock issued under employee stock option and stock purchase plans	[1]	2,716			$ 281	2,435
Common stock issued under employee stock option and stock purchase plans (in shares)	[1]				563,091
Benefit plan stock sales (purchases), net	[2]	(1)				(1)
Benefit plan stock sales (purchases), net (in shares)	[2]				50
Common stock repurchases		(21,220)			$ (173)	(6,940)	(14,107)
Common stock repurchases (in shares)					(345,114)
Share-based compensation		14,922				14,922
Ending balance at Jun. 30, 2019		2,607,706		0	$ 26,667	1,094,807	2,385,620		(899,388)
Ending balance (in shares) at Jun. 30, 2019					53,334,512
Beginning balance at Mar. 31, 2019		2,566,804		0	$ 26,651	1,086,714	2,343,857		(890,418)
Beginning balance (in shares) at Mar. 31, 2019					53,300,205
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		66,245					75,215		(8,970)
Common stock dividends declared and paid		(28,849)					(28,849)
Common stock issued under employee stock option and stock purchase plans	[3]	3,058			$ 76	2,982
Common stock issued under employee stock option and stock purchase plans (in shares)	[3]				153,797
Benefit plan stock sales (purchases), net	[4]	(11)				(11)
Benefit plan stock sales (purchases), net (in shares)	[4]				(220)
Common stock repurchases		(7,064)			$ (60)	(2,401)	(4,603)
Common stock repurchases (in shares)					(119,270)
Share-based compensation		7,523				7,523
Ending balance at Jun. 30, 2019		2,607,706		0	$ 26,667	1,094,807	2,385,620		(899,388)
Ending balance (in shares) at Jun. 30, 2019					53,334,512
Beginning balance at Dec. 31, 2019		$ 2,476,310	$ (5,077)	0	$ 26,639	1,108,649	2,177,513	$ (5,077)	(836,491)
Beginning balance (in shares) at Dec. 31, 2019		53,278,316			53,278,316
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		$ (251,861)					(183,712)		(68,149)
Common stock dividends declared and paid		(60,226)					(60,226)
Common stock issued under employee stock option and stock purchase plans	[1]	1,213			$ 422	791
Common stock issued under employee stock option and stock purchase plans (in shares)	[1]				843,403
Benefit plan stock sales (purchases), net	[2]	27				27
Benefit plan stock sales (purchases), net (in shares)	[2]				220
Common stock repurchases		(11,924)			$ (152)	(6,214)	(5,558)
Common stock repurchases (in shares)					(303,098)
Share-based compensation		10,630				10,630
Ending balance at Jun. 30, 2020		$ 2,159,092		0	$ 26,909	1,113,883	1,922,940		(904,640)
Ending balance (in shares) at Jun. 30, 2020		53,818,841			53,818,841
Beginning balance at Mar. 31, 2020		$ 2,242,736		0	$ 26,867	1,103,928	2,026,886		(914,945)
Beginning balance (in shares) at Mar. 31, 2020					53,735,964
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		(63,794)					(74,099)		10,305
Common stock dividends declared and paid		(29,847)					(29,847)
Common stock issued under employee stock option and stock purchase plans	[3]	2,470			$ 42	2,428
Common stock issued under employee stock option and stock purchase plans (in shares)	[3]				83,145
Benefit plan stock sales (purchases), net	[4]	(12)				(12)
Benefit plan stock sales (purchases), net (in shares)	[4]				(268)
Common stock repurchases		0
Share-based compensation		7,539				7,539
Ending balance at Jun. 30, 2020		$ 2,159,092		$ 0	$ 26,909	$ 1,113,883	$ 1,922,940		$ (904,640)
Ending balance (in shares) at Jun. 30, 2020		53,818,841			53,818,841

[1] Net of common shares withheld as payment for the exercise price or to satisfy the holders’ withholding tax liability upon exercise of options.

[2] Represents open-market transactions of common shares by the trustee of our deferred compensation plans

[3] Net of common shares withheld as payment for the exercise price or to satisfy the holders’ withholding tax liability upon exercise of options.

[4] Represents open-market transactions of common shares by the trustee of our deferred compensation plans.