Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment		Cumulative Effect, Period Of Adoption, Adjusted Balance	Preferred Stock	Preferred Stock Cumulative Effect, Period Of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period Of Adoption, Adjusted Balance	Additional Paid-In Capital	Additional Paid-In Capital Cumulative Effect, Period Of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period Of Adoption, Adjusted Balance	Retained Earnings	Retained Earnings Cumulative Effect, Period Of Adoption, Adjustment		Retained Earnings Cumulative Effect, Period Of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period Of Adoption, Adjusted Balance
Beginning balance at Dec. 31, 2018	$ 5,415,177	$ (497)	[1]	$ 5,414,680	$ 0	$ 0	$ 121,218	$ 121,218	$ 524,414	$ 524,414	$ 319,475	$ 319,475	$ 5,213,468	$ (497)	[1]	$ 5,212,971	$ (763,398)	$ (763,398)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	735,937										550,592		185,345
Common dividends declared	(18,943)												(18,943)
Acquisition of treasury stock	(110,896)																(110,896)
Stock-based compensation	10,559								(5,885)				(6,817)				23,261
Exercise of stock options	12,089												(7,736)				19,825
Ending balance at Mar. 31, 2019	6,043,426	105			0		121,218		518,529		870,067		5,364,820	105			(831,208)
Beginning balance at Dec. 31, 2018	5,415,177	(497)	[1]	5,414,680	0	0	121,218	121,218	524,414	524,414	319,475	319,475	5,213,468	(497)	[1]	$ 5,212,971	(763,398)	(763,398)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	1,491,686
Ending balance at Jun. 30, 2019	6,700,398				0		121,218		526,518		1,439,250		5,514,517				(901,105)
Beginning balance at Mar. 31, 2019	6,043,426	105			0		121,218		518,529		870,067		5,364,820	105			(831,208)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	755,749										569,183		186,566
Common dividends declared	(18,838)												(18,838)
Acquisition of treasury stock	(119,201)																(119,201)
Stock-based compensation	11,256								7,989				0				3,267
Exercise of stock options	27,901												(18,136)				46,037
Ending balance at Jun. 30, 2019	$ 6,700,398				0		121,218		526,518		1,439,250		5,514,517				(901,105)
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Beginning balance at Dec. 31, 2019	$ 7,294,307	(454)	[2]	7,293,853	0	0	117,218	117,218	531,554	531,554	1,844,830	1,844,830	5,551,329	(454)	[2]		(750,624)	(750,624)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	(613,043)										(778,583)		165,540
Common dividends declared	(19,963)												(19,963)
Acquisition of treasury stock	(166,729)																(166,729)
Stock-based compensation	9,356								(12,126)				(482)				21,964
Exercise of stock options	16,808												(9,539)				26,347
Ending balance at Mar. 31, 2020	6,520,282				0		117,218		519,428		1,066,247		5,686,431				(869,042)
Beginning balance at Dec. 31, 2019	7,294,307	$ (454)	[2]	$ 7,293,853	0	$ 0	117,218	$ 117,218	531,554	$ 531,554	1,844,830	$ 1,844,830	5,551,329	$ (454)	[2]		(750,624)	$ (750,624)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	725,651
Ending balance at Jun. 30, 2020	$ 7,848,369				0		117,218		528,060		2,231,893		5,838,930				(867,732)
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance at Mar. 31, 2020	$ 6,520,282				0		117,218		519,428		1,066,247		5,686,431				(869,042)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	1,338,694										1,165,646		173,048
Common dividends declared	(19,956)												(19,956)
Stock-based compensation	8,632								8,632
Exercise of stock options	717												(593)				1,310
Ending balance at Jun. 30, 2020	$ 7,848,369				$ 0		$ 117,218		$ 528,060		$ 2,231,893		$ 5,838,930				$ (867,732)
Increase (Decrease) in Stockholders' Equity
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member

[1] Adoption of ASU 2016-02, Leases (Topic 842), on January 1, 2019.

[2] Adoption of Accounting Standard Update (ASU) 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, on January 1, 2020. See more information in Note 2—New Accounting Standards.