Parent Company Condensed Financial Statements (Condensed Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents due from subsidiary bank	$ 4,017,971	$ 3,261,149
Other assets	1,324,262	917,095
TOTAL	52,156,913	44,196,096	$ 41,042,356
LIABILITIES
Total liabilities	46,887,738	39,178,479
STOCKHOLDERS’ EQUITY
Common stock, $0.001 par value, 200,000,000 shares authorized; 167,240,600 and 166,621,959 shares issued in 2020 and 2019, respectively	167	167
Additional paid-in capital	1,858,352	1,826,345
Retained earnings	4,000,414	3,689,377
Treasury stock, at cost 25,675,371 shares in 2020 and 20,996,574 shares in 2019	(634,083)	(479,864)
AOCI, net of tax	44,325	(18,408)
Total stockholders’ equity	5,269,175	5,017,617	$ 4,423,974	$ 3,841,951
TOTAL	52,156,913	44,196,096
Parent Company
ASSETS
Cash and cash equivalents due from subsidiary bank	439,065	166,131
Investments in tax credit and other investments, net	6,586	11,637
Other assets	3,072	4,091
TOTAL	5,504,357	5,175,155
LIABILITIES
Long-term debt	147,376	147,101
Accrued income tax payable	81,741	4,534
Other liabilities	6,065	5,903
Total liabilities	235,182	157,538
STOCKHOLDERS’ EQUITY
Common stock, $0.001 par value, 200,000,000 shares authorized; 167,240,600 and 166,621,959 shares issued in 2020 and 2019, respectively	167	167
Additional paid-in capital	1,858,352	1,826,345
Retained earnings	4,000,414	3,689,377
Treasury stock, at cost 25,675,371 shares in 2020 and 20,996,574 shares in 2019	(634,083)	(479,864)
AOCI, net of tax	44,325	(18,408)
Total stockholders’ equity	5,269,175	5,017,617
TOTAL	5,504,357	5,175,155
Parent Company | Bank
ASSETS
Investments in Subsidiaries	5,048,896	4,987,666
Parent Company | Nonbank
ASSETS
Investments in Subsidiaries	$ 6,738	$ 5,630