Condensed Financial Statements of Parent Company (Statements of Financial Condition) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 698,567	$ 459,606	$ 492,000	$ 437,334
Equity investments	49,090	49,835
Other assets	69,206	48,821
Total assets	15,667,440	15,305,952
LIABILITIES:
Convertible notes, net	199,458	194,543
Subordinated debentures, net	103,035	101,929
Total liabilities	13,631,429	13,402,741
STOCKHOLDERS’ EQUITY	2,036,011	1,903,211	1,928,255	1,855,473
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	15,667,440	15,305,952
Parent Company
ASSETS
Cash and cash equivalents	38,981	12,593	$ 13,327	$ 13,859
Equity investments	0	525
Other assets	6,703	5,704
Investment in bank subsidiary	2,294,175	2,181,959
Total assets	2,339,859	2,200,781
LIABILITIES:
Convertible notes, net	199,458	194,543
Subordinated debentures, net	103,035	101,929
Accounts payable and other liabilities	1,355	1,098
Total liabilities	303,848	297,570
STOCKHOLDERS’ EQUITY	2,036,011	1,903,211
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 2,339,859	$ 2,200,781