Condensed Statements of Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS:
Cash and cash equivalents	$ 1,474,955	$ 2,528,169	$ 557,850	$ 537,674
Other assets	358,161	401,138
Total assets	51,899,376	49,124,195
LIABILITIES AND STOCKHOLDERS' EQUITY:
Junior subordinated debentures	359,508	359,179
Other liabilities	271,845	312,977
Total liabilities	45,244,141	42,328,819
Stockholders' equity	6,655,235	6,795,376	6,123,991
Total liabilities and stockholders' equity	51,899,376	49,124,195
Parent Company
ASSETS:
Cash and cash equivalents	228,618	90,536	$ 63,727	$ 70,380
Investments in subsidiaries	7,064,341	7,050,139
Receivables from subsidiaries	6,455	4,750
Other assets	23,724	23,980
Total assets	7,323,138	7,169,405
LIABILITIES AND STOCKHOLDERS' EQUITY:
Junior subordinated debentures	359,508	359,179
Subordinated notes	294,697
Other liabilities	13,698	14,850
Total liabilities	667,903	374,029
Stockholders' equity	6,655,235	6,795,376
Total liabilities and stockholders' equity	$ 7,323,138	$ 7,169,405