Parent Company Information (Components of Condensed Balance Sheets The Parent Company) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 263,104	$ 257,895	$ 329,499	$ 256,786
Intercompany debt securities		150,000
Other assets	626,551	455,380
Total Assets	32,590,690	30,389,344
Liabilities and shareholders’ equity:
Liabilities	29,356,065	27,181,574
Total liabilities and shareholders' equity	32,590,690	30,389,344
Parent Company [Member]
Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	302,315	510,940	$ 317,473	$ 181,085
Intercompany debt securities	150,000
Investment in subsidiaries	3,340,556	3,079,549
Alternative investments	8,970	5,356
Other assets	8,122	13,537
Total Assets	3,809,963	3,759,382
Liabilities and shareholders’ equity:
Senior notes	490,343	463,044
Junior subordinated debt	77,320	77,320
Accrued interest payable	5,862	6,057
Due to subsidiaries	324	52
Other liabilities	1,489	5,139
Liabilities	575,338	551,612
Shareholders’ equity	3,234,625	3,207,770
Total liabilities and shareholders' equity	$ 3,809,963	$ 3,759,382