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		161,930					161,930
Issuance of stock		1,994				1,994
Dividends declared:
Common stock	[1]	(69,168)					(69,168)
Preferred stock		(1,053)					(1,053)
Common stock purchases	[2]	(503,482)				76,336			(579,818)
Common stock reissuance		4,591				(1,111)			5,702
Preferred stock redemption	[3]	(28,017)			(28,017)
Stock based compensation		13,146				(4,298)			17,444
Other comprehensive loss, net of tax		389,287								389,287
Ending balance at Jun. 30, 2020		5,780,165		1,044	22,143	4,520,333	2,033,782		(1,016,486)	219,349
Beginning balance at Mar. 31, 2020		5,669,605		1,044	22,143	4,366,300	1,940,170		(870,675)	210,623
Increase Decrease In Stockholders Equity [Roll Forward]
Net income		127,628					127,628
Issuance of stock		1,131				1,131
Dividends declared:
Common stock	[4]	(33,663)					(33,663)
Preferred stock		(353)					(353)
Common stock purchases	[2]	(681)				153,402			(154,083)
Common stock reissuance		1,485				(548)			2,033
Stock based compensation		6,287				48			6,239
Other comprehensive loss, net of tax		8,726								8,726
Ending balance at Jun. 30, 2020		5,780,165		1,044	22,143	4,520,333	2,033,782		(1,016,486)	219,349
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		480,711					480,711
Issuance of stock		2,226				2,226
Dividends declared:
Common stock	[1]	(70,048)					(70,048)
Preferred stock		(706)					(706)
Common stock purchases	[5]	(355,307)				(70,000)			(285,307)
Stock based compensation		14,733				2,899			11,834
Other comprehensive loss, net of tax		(285,682)								(285,682)
Ending balance at Jun. 30, 2021		5,814,614		1,045	22,143	4,506,659	2,670,885		(1,290,427)	(95,691)
Beginning balance at Mar. 31, 2021		5,897,559		1,045	22,143	4,571,919	2,489,453		(1,012,263)	(174,738)
Increase Decrease In Stockholders Equity [Roll Forward]
Net income		218,079					218,079
Issuance of stock		1,108				1,108
Dividends declared:
Common stock	[4]	(36,294)					(36,294)
Preferred stock		(353)					(353)
Common stock purchases	[5]	(351,365)				(70,000)			(281,365)
Stock based compensation		6,833				3,632			3,201
Other comprehensive loss, net of tax		79,047								79,047
Ending balance at Jun. 30, 2021		$ 5,814,614		$ 1,045	$ 22,143	$ 4,506,659	$ 2,670,885		$ (1,290,427)	$ (95,691)

[1] Dividends declared per common share during the six months ended June 30, 2021 - $0.85 (2020 - $0.80).

[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 June 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. Refer to Note 17 for additional information.