CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Paid-in capital	Treasury stock	Accumulated other comprehensive income (loss)	Retained earnings
Balance, beginning of period at Dec. 31, 2018		$ 371,353	$ 1,862,536	$ (175,059)	$ (124,214)	$ 1,647,275
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reacquisition of convertible junior subordinated debentures-equity component			0
Reissuance of treasury stock, net under share-based compensation plans			(11,715)	5,989
Equity compensation			14,152
Repurchase of common stock				(94,126)
Other comprehensive (loss) income, net of tax	$ 187,996				187,996
Net income	496,653					496,653
Cash dividends						(21,223)
Balance, end of period at Sep. 30, 2019	4,159,617	371,353	1,864,973	(263,196)	63,782	2,122,705
Balance, beginning of period at Jun. 30, 2019		371,353	1,860,578	(194,070)	30,810	1,966,994
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reacquisition of convertible junior subordinated debentures-equity component			0
Reissuance of treasury stock, net under share-based compensation plans			(133)	59
Equity compensation			4,528
Repurchase of common stock				(69,185)
Other comprehensive (loss) income, net of tax	32,972				32,972
Net income	176,934					176,934
Cash dividends						(21,223)
Balance, end of period at Sep. 30, 2019	4,159,617	371,353	1,864,973	(263,196)	63,782	2,122,705
Balance, beginning of period at Dec. 31, 2019	4,309,234	371,353	1,869,719	(283,196)	72,708	2,278,650
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reacquisition of convertible junior subordinated debentures-equity component			(2,673)
Reissuance of treasury stock, net under share-based compensation plans			(18,807)	9,867
Equity compensation			8,331
Repurchase of common stock				(119,997)
Other comprehensive (loss) income, net of tax	95,069				95,069
Net income	294,663					294,663
Cash dividends						(62,065)
Balance, end of period at Sep. 30, 2020	4,513,622	371,353	1,856,570	(393,326)	167,777	2,511,248
Balance, beginning of period at Jun. 30, 2020		371,353	1,859,195	(393,425)	145,412	2,400,820
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reacquisition of convertible junior subordinated debentures-equity component			(2,673)
Reissuance of treasury stock, net under share-based compensation plans			(140)	99
Equity compensation			188
Repurchase of common stock				0
Other comprehensive (loss) income, net of tax	22,365				22,365
Net income	130,811					130,811
Cash dividends						(20,383)
Balance, end of period at Sep. 30, 2020	$ 4,513,622	$ 371,353	$ 1,856,570	$ (393,326)	$ 167,777	$ 2,511,248