CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common stock	Paid-in capital	Paid-in capital Cumulative Effect, Period of Adoption, Adjustment	Paid-in capital Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury stock	Accumulated other comprehensive income (loss)	Retained earnings	Retained earnings Cumulative Effect, Period of Adoption, Adjustment	Retained earnings Cumulative Effect, Period of Adoption, Adjusted Balance
Balance, beginning of period at Dec. 31, 2019		$ 371,353	$ 1,869,719			$ (283,196)	$ 72,708	$ 2,278,650
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reissuance of treasury stock, net under share-based compensation plans			(18,807)			9,867
Reacquisition of convertible junior subordinated debentures - equity component			(2,673)
Equity compensation			8,331
Repurchase of common stock						(119,997)
Other comprehensive income (loss), 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]
Reissuance of treasury stock, net under share-based compensation plans			(140)			99
Reacquisition of convertible junior subordinated debentures - equity component			(2,673)
Equity compensation			188
Repurchase of common stock						0
Other comprehensive income (loss), 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
Balance, beginning of period at Dec. 31, 2020	4,698,986	371,353	1,862,042	$ (68,289)	$ 1,793,753	(393,326)	216,821	2,642,096	$ 68,289	$ 2,710,385
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reissuance of treasury stock, net under share-based compensation plans			(15,956)			8,879
Reacquisition of convertible junior subordinated debentures - equity component			0
Equity compensation			12,077
Repurchase of common stock						(150,000)
Other comprehensive income (loss), net of tax	(69,176)						(69,176)
Net income	461,049							461,049
Cash dividends								(68,439)
Balance, end of period at Sep. 30, 2021	4,877,420	371,353	1,789,874			(534,447)	147,645	3,102,995
Balance, beginning of period at Jun. 30, 2021		371,353	1,786,260			(384,550)	169,282	2,972,362
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reissuance of treasury stock, net under share-based compensation plans			(211)			103
Reacquisition of convertible junior subordinated debentures - equity component			0
Equity compensation			3,825
Repurchase of common stock						(150,000)
Other comprehensive income (loss), net of tax	(21,637)						(21,637)
Net income	157,977							157,977
Cash dividends								(27,344)
Balance, end of period at Sep. 30, 2021	$ 4,877,420	$ 371,353	$ 1,789,874			$ (534,447)	$ 147,645	$ 3,102,995