Parent Company Information (Components of Condensed Balance Sheets The Parent Company) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 257,895	$ 329,499
Intercompany debt securities		150,000
Other assets	455,380	313,256
Total assets	30,389,344	27,610,315
Liabilities and shareholders’ equity:
Total liabilities	27,181,574	24,723,800
Total liabilities and shareholders' equity	30,389,344	27,610,315
Parent Company [Member]
Assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	510,940	317,473
Intercompany debt securities	150,000
Investment in subsidiaries	3,079,549	2,633,848
Due from subsidiaries	0	36
Alternative investments	5,356	3,252
Other assets	13,537	12,003
Total assets	3,759,382	3,116,612
Liabilities and shareholders’ equity:
Senior notes	463,044	148,701
Junior subordinated debt	77,320	77,320
Accrued interest payable	6,057	2,664
Due to subsidiaries	52	0
Other liabilities	5,139	1,412
Total liabilities	551,612	230,097
Shareholders’ equity	3,207,770	2,886,515
Total liabilities and shareholders' equity	$ 3,759,382	$ 3,116,612