Consolidated Statements of Equity (Unaudited) - USD ($)	Total	Series C Preferred Stock	Total	Total Series C Preferred Stock	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Series C Preferred Stock	Accumulated Other Comprehensive Income (Loss)	Other	Non-controlling Interest
Balance (in shares) at Dec. 31, 2018					7,000	88,198,460
Balance at Dec. 31, 2018	$ 2,556,260,000		$ 2,537,801,000		$ 169,302,000	$ 88,198,000	$ 798,627,000	$ 1,766,994,000		$ (33,138,000)	$ (252,182,000)	$ 18,459,000
Increase (Decrease) in Equity
Net income	73,449,000		70,494,000					70,494,000				2,955,000
Other comprehensive income (loss), net of tax	38,619,000		38,619,000							38,619,000
Net investment by (distribution to) non-controlling interest	8,038,000											8,038,000
Dividends on 5.70% Series C Preferred Stock		$ (2,493,000)		$ (2,493,000)					$ (2,493,000)
Dividends on common stock	(24,294,000)		(24,294,000)					(24,294,000)
Stock compensation plans, net of tax (in shares)						(135,422)
Stock compensation plans, net of tax	(3,734,000)		(3,734,000)			$ (135,000)	(10,390,000)				6,791,000
Change in shares held in trust for deferred compensation plans, at cost							1,230,000				(1,230,000)
Balance (in shares) at Mar. 31, 2019					7,000	88,063,038
Balance at Mar. 31, 2019	2,645,845,000		2,616,393,000		$ 169,302,000	$ 88,063,000	789,467,000	1,810,701,000		5,481,000	(246,621,000)	29,452,000
Increase (Decrease) in Equity
Change in accounting principle	(159,249,000)		(159,323,000)					(159,323,000)				74,000
Adjusted balance after cumulative adjustment related to change in accounting principle	5,567,992,000		5,547,692,000		$ 169,302,000	$ 152,966,000	3,462,080,000	1,737,104,000		54,277,000	(28,037,000)	20,300,000
Balance (in shares) at Dec. 31, 2019					7,000	152,965,571
Balance at Dec. 31, 2019	5,727,241,000		5,707,015,000		$ 169,302,000	$ 152,966,000	3,462,080,000	1,896,427,000		54,277,000	(28,037,000)	20,226,000
Increase (Decrease) in Equity
Net income	53,816,000		51,899,000					51,899,000				1,917,000
Other comprehensive income (loss), net of tax	111,893,000		111,893,000							111,893,000
Net investment by (distribution to) non-controlling interest	7,932,000											7,932,000
Repurchases of shares of common stock	(33,098,000)		(33,098,000)			$ (873,376)	(32,225,000)
Dividends on 5.70% Series C Preferred Stock		$ (2,493,000)		$ (2,493,000)					$ (2,493,000)
Dividends on common stock	(53,578,000)		(53,578,000)					(53,578,000)
Stock compensation plans, net of tax (in shares)						93,789
Stock compensation plans, net of tax	3,369,000		3,369,000			$ 93,000	3,276,000				0
Change in shares held in trust for deferred compensation plans, at cost							103,000				(103,000)
Balance (in shares) at Mar. 31, 2020					7,000	152,185,984
Balance at Mar. 31, 2020	$ 5,655,833,000		$ 5,625,684,000		$ 169,302,000	$ 152,186,000	$ 3,433,234,000	$ 1,732,932,000		$ 166,170,000	$ (28,140,000)	$ 30,149,000