Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance, beginning of period (in shares) at Dec. 31, 2016		180,595,054
Balance, beginning of period at Dec. 31, 2016	$ 1,920,158	$ 1,806	$ 1,381,862	$ 1,337,673	$ (565,381)	$ (235,802)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	521,759			521,759
Other comprehensive income (loss), net of tax	65,332				65,332
Dividends	(251,862)			(251,862)
Repurchase of common stock	$ (465,263)					(465,263)
Options granted during period (in shares)	0
Share-based compensation	$ 42,800		29,600			13,200
Issuance of nonvested stock (in shares)		408,950
Issuance of nonvested stock	0	$ 4	(4)
Exercise of stock options (in shares)		282,543
Exercise of stock options	11,353	$ 3	11,350
Balance, end of period (in shares) at Dec. 31, 2017		181,286,547
Balance, end of period at Dec. 31, 2017	1,844,277	$ 1,813	1,422,808	1,607,570	(500,049)	(687,865)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	531,451			531,451
Other comprehensive income (loss), net of tax	(21,287)				(21,287)
Dividends	(245,810)			(245,810)
Repurchase of common stock	$ (390,606)					(390,606)
Options granted during period (in shares)	0
Share-based compensation	$ 46,375		33,293			13,082
Issuance of nonvested stock (in shares)		485,005
Issuance of nonvested stock	0	$ 4	(4)
Exercise of stock options (in shares)		159,673
Exercise of stock options	3,525	$ 2	3,523
Reclassification of certain tax effects	0			108,348	(108,348)
Balance, end of period (in shares) at Dec. 31, 2018		181,931,225
Balance, end of period at Dec. 31, 2018	1,773,949	$ 1,819	1,459,620	2,007,583	(629,684)	(1,065,389)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	423,635			423,635
Other comprehensive income (loss), net of tax	92,735				92,735
Dividends	(237,221)			(237,221)
Repurchase of common stock	$ (296,520)					(296,520)
Options granted during period (in shares)	0
Share-based compensation	$ 43,832		27,804			16,028
Issuance of nonvested stock (in shares)		715,579
Issuance of nonvested stock	$ 0	$ 7	(7)
Exercise of stock options (in shares)	168,000	169,732
Exercise of stock options	$ 3,589	$ 2	3,587
Balance, end of period (in shares) at Dec. 31, 2019		182,816,536
Balance, end of period at Dec. 31, 2019	$ 1,803,999	$ 1,828	$ 1,491,004	$ 2,193,997	$ (536,949)	$ (1,345,881)