Regulatory Capital Ratios for in Comparison With Minimum Amounts and Ratios Required by Federal Reserve Board of Governors (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Common Equity, Tier 1 Amount
Total regulatory capital, Common Equity, Tier 1 Amount	$ 3,558,415
Minimum for capital adequacy purposes, Common Equity, Tier 1 Amount	1,526,064
Excess, Common Equity, Tier 1 Amount	$ 2,032,351
Common Equity, Tier 1 Ratio
Total regulatory capital, Common Equity, Tier 1 Ratio	10.49%
Minimum for capital adequacy purposes, Common Equity, Tier 1 Ratio	4.50%
Excess, Common Equity, Tier 1 Ratio	5.99%
Leverage Capital, Amount
Total regulatory capital, Leverage Capital, Amount	$ 3,644,872	$ 3,731,430
Minimum for capital adequacy purposes, Leverage Capital, Amount	1,876,006	1,856,755
Excess, Leverage Capital, Amount	$ 1,768,866	$ 1,874,675
Leverage Capital, Ratio
Total regulatory capital, Leverage Capital, Ratio	7.77%	8.04%
Minimum for capital adequacy purposes, Leverage Capital, Ratio	4.00%	4.00%
Excess, Leverage Capital, Ratio	3.77%	4.04%
Risk-Based Capital, Tier 1 Amount
Total regulatory capital, Risk-Based Capital, Tier 1 Amount	$ 3,644,872	$ 3,731,430
Minimum for capital adequacy purposes, Risk-Based Capital, Tier 1 Amount	2,034,752	1,213,802
Excess, Risk-Based Capital, Tier 1 Amount	$ 1,610,120	$ 2,517,628
Risk-Based Capital, Tier 1 Ratio
Total regulatory capital, Risk-Based Capital, Tier 1 Ratio	10.75%	12.30%
Minimum for capital adequacy purposes, Risk-Based Capital, Tier 1 Ratio	6.00%	4.00%
Excess, Risk-Based Capital, Tier 1 Ratio	4.75%	8.30%
Risk-Based Capital, Total Amount
Total regulatory capital, Risk-Based Capital, Total Amount	$ 4,086,913	$ 3,919,248
Minimum for capital adequacy purposes, Risk-Based Capital, Total Amount	2,713,003	2,427,605
Excess, Risk-Based Capital, Total Amount	$ 1,373,910	$ 1,491,643
Risk-Based Capital, Total Ratio
Total regulatory capital, Risk-Based Capital, Total Ratio	12.05%	12.92%
Minimum for capital adequacy purposes, Risk-Based Capital, Total Ratio	8.00%	8.00%
Excess, Risk-Based Capital, Total Ratio	4.05%	4.92%