Condensed Statements of Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS:
Cash and cash equivalents	$ 537,674	$ 564,150	$ 644,550	$ 2,427,258
Securities available for sale	204,255	173,783
Other assets	635,316	338,307
Total assets	50,317,796	48,559,217
LIABILITIES AND STOCKHOLDERS' EQUITY:
Junior subordinated debentures	358,605	358,355
Other liabilities	207,937	222,181
Total liabilities	44,383,100	42,777,402
Stockholders' equity	5,934,696	5,781,815	5,735,662
Total liabilities and stockholders' equity	50,317,796	48,559,217
Parent Company
ASSETS:
Cash and cash equivalents	70,380	89,518	$ 126,165	$ 113,745
Securities available for sale	1,968	2,002
Investments in subsidiaries	6,232,228	6,039,718
Receivables from subsidiaries	7,635	7,859
Other assets	34,418	32,165
Total assets	6,346,629	6,171,262
LIABILITIES AND STOCKHOLDERS' EQUITY:
Junior subordinated debentures	358,605	358,355
Other liabilities	53,328	31,092
Total liabilities	411,933	389,447
Stockholders' equity	5,934,696	5,781,815
Total liabilities and stockholders' equity	$ 6,346,629	$ 6,171,262