CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total	Cumulative effect adoption adjustment	Common Stock	Preferred Stock	Capital surplus	Retained earnings	Retained earnings Cumulative effect adoption adjustment	Treasury stock	Accumulated other comprehensive income (loss)
Beginning balance at Dec. 31, 2019		$ 6,016,779	$ (205,842)	$ 1,044	$ 50,160	$ 4,447,412	$ 2,147,915	$ (205,842)	$ (459,814)	$ (169,938)
Increase Decrease In Stockholders Equity [Roll Forward]
Net income		330,346					330,346
Issuance of stock		3,140		1		3,139
Dividends declared:
Common stock	[1]	(102,861)					(102,861)
Preferred stock		(1,405)					(1,405)
Common stock purchases	[2]	(503,667)				76,336			(580,003)
Common stock reissuance		4,791				(1,180)			5,971
Preferred stock redemption	[3]	(28,017)			(28,017)
Stock based compensation		13,467				(4,018)			17,485
Other comprehensive loss, net of tax		385,354								385,354
Ending balance at Sep. 30, 2020		5,912,085		1,045	22,143	4,521,689	2,168,153		(1,016,361)	215,416
Beginning balance at Jun. 30, 2020		5,780,165		1,044	22,143	4,520,333	2,033,782		(1,016,486)	219,349
Increase Decrease In Stockholders Equity [Roll Forward]
Net income		168,416					168,416
Issuance of stock		1,146		1		1,145
Dividends declared:
Common stock	[4]	(33,693)					(33,693)
Preferred stock		(352)					(352)
Common stock purchases		(185)				0			(185)
Common stock reissuance		200				(69)			269
Stock based compensation		321				280			41
Other comprehensive loss, net of tax		(3,933)								(3,933)
Ending balance at Sep. 30, 2020		5,912,085		1,045	22,143	4,521,689	2,168,153		(1,016,361)	215,416
Beginning balance at Dec. 31, 2020		6,028,687		1,045	22,143	4,571,534	2,260,928		(1,016,954)	189,991
Increase Decrease In Stockholders Equity [Roll Forward]
Net income		728,825					728,825
Issuance of stock		3,461		1		3,460
Dividends declared:
Common stock	[1]	(106,354)					(106,354)
Preferred stock		(1,059)					(1,059)
Common stock purchases	[5]	(355,571)				(8,557)			(347,014)
Stock based compensation		15,068				3,204			11,864
Other comprehensive loss, net of tax		(330,086)								(330,086)
Ending balance at Sep. 30, 2021		5,982,971		1,046	22,143	4,569,641	2,882,340		(1,352,104)	(140,095)
Beginning balance at Jun. 30, 2021		5,814,614		1,045	22,143	4,506,659	2,670,885		(1,290,427)	(95,691)
Increase Decrease In Stockholders Equity [Roll Forward]
Net income		248,114					248,114
Issuance of stock		1,235		1		1,234
Dividends declared:
Common stock	[4]	(36,306)					(36,306)
Preferred stock		(353)					(353)
Common stock purchases	[6]	(264)				61,443			(61,707)
Stock based compensation		335				305			30
Other comprehensive loss, net of tax		(44,404)								(44,404)
Ending balance at Sep. 30, 2021		$ 5,982,971		$ 1,046	$ 22,143	$ 4,569,641	$ 2,882,340		$ (1,352,104)	$ (140,095)

[1] Dividends declared per common share during the nine months ended September 30, 2021 - $1.30 (2020 - $1.20).

[2] During the quarter ended June 30, 2020, the Corporation completed a $500 million accelerated share repurchase transaction with respect to its common stock, which was accounted for as a treasury stock transaction. Refer to Note 17 for additional information.

[3] On February 24, 2020, the Corporation redeemed all the outstanding shares of 2008 Series B Preferred Stock. Refer to Note 17 for additional information.

[4] Dividends declared per common share during the quarter ended September 30, 2021 - $0.45 (2020 - $0.40).

[5] During the quarter ended June 30, 2021, the Corporation entered into a $350 million accelerated share repurchase transaction with respect to its common stock, which was accounted for as a treasury stock transaction. The transaction was completed on September 9, 2021. Refer to Note 17 for additional information.

[6] During the quarter ended September 30, 2021, the Corporation completed its previously announced $350 million accelerated share repurchase transaction with respect to its common stock. Refer to Note 17 for additional information.