Consolidated Statement of Shareholder Equity Statement - USD ($) $ in Thousands	Total	Series E Preferred Stock [Member]	Series F Preferred Stock [Member]	Common Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series E Preferred Stock [Member]	Preferred Stock [Member] Series F Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series E Preferred Stock [Member]	Retained Earnings [Member] Series F Preferred Stock [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]
Beginning Balance at Dec. 31, 2016	$ 2,527,012				$ 122,710			$ 937	$ 1,125,937	$ 1,425,320			$ (70,899)	$ (76,993)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	255,439									255,439
Other Comprehensive Income (Loss), Net of Tax	1,110													1,110
Common Stock, Dividends, Per Share, Declared				$ 1.03
Dividends, Common Stock	94,929								168	(95,097)
Preferred Stock, Dividends Per Share, Declared		$ 1,600.00
Dividends, Preferred Stock		$ 8,096									$ (8,096)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	14,184									2,636			11,548
Stock Issued During Period, Value, Stock Options Exercised	8,259								(3,941)				12,200
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	11,694												(11,694)
Stock Repurchased During Period, Value	11,585												(11,585)
Stockholders' Equity, Other			$ (88)									$ (88)
Ending Balance at Dec. 31, 2017	2,701,958				145,056			937	1,122,164	1,595,762			(70,430)	(91,531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	(39,121)													(39,121)
Ending Balance at Sep. 30, 2018														(130,652)
Beginning Balance at Dec. 31, 2017	2,701,958				145,056			937	1,122,164	1,595,762			(70,430)	(91,531)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	360,418									360,418
Other Comprehensive Income (Loss), Net of Tax	(39,121)													(39,121)
Common Stock, Dividends, Per Share, Declared				1.25
Dividends, Common Stock	115,343								99	(115,442)
Preferred Stock, Dividends Per Share, Declared			$ 1,323.4375
Dividends, Preferred Stock			$ 7,875									(7,875)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	11,612								(1,541)	3,275			9,878
Stock Issued During Period, Value, Stock Options Exercised	2,173								(5,762)				7,935
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	13,779												(13,779)
Stock Repurchased During Period, Value	12,158												(12,158)
Stock Issued During Period, Value, Other			(19)
Stockholders' Equity, Other			22									22
Stock Redeemed or Called During Period, Value		$ 122,710				$ 122,710
Stock Issued During Period, Value, New Issues			$ 145,056				$ 145,056
Ending Balance at Dec. 31, 2018	2,886,515				145,037			937	1,114,394	1,828,303			(71,504)	(130,652)
Beginning Balance at Sep. 30, 2018														(130,652)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	98,838
Ending Balance at Dec. 31, 2018	2,886,515				145,037			937	1,114,394	1,828,303			(71,504)	(130,652)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other Comprehensive Income (Loss), Net of Tax	94,580													94,580
Ending Balance at Sep. 30, 2019														(36,072)
Beginning Balance at Dec. 31, 2018	2,886,515				145,037			937	1,114,394	1,828,303			(71,504)	(130,652)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	382,723									382,723
Other Comprehensive Income (Loss), Net of Tax	94,580													94,580
Common Stock, Dividends, Per Share, Declared				$ 1.53
Dividends, Common Stock	141,286									(141,286)
Preferred Stock, Dividends Per Share, Declared			$ 1,312.50
Dividends, Preferred Stock			$ 7,875									$ (7,875)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	12,626								885	0			11,741
Stock Issued During Period, Value, Stock Options Exercised	619								(2,029)				2,648
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	6,616												(6,616)
Stock Repurchased During Period, Value	13,003												(13,003)
Stock Issued During Period, Value, Conversion of Units	0								(566)	(6,484)			7,050
Ending Balance at Dec. 31, 2019	3,207,770				145,037			937	1,113,250	2,061,352			(76,734)	(36,072)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-08 [Member]	(513)									(513)
Beginning Balance at Sep. 30, 2019														(36,072)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	90,473
Ending Balance at Dec. 31, 2019	$ 3,207,770				$ 145,037			$ 937	$ 1,113,250	$ 2,061,352			$ (76,734)	$ (36,072)