Income taxes (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income taxes expense difference from the amount computed by applying the statutory federal income tax rate to pre-tax income
Income taxes at statutory rate	$ 428,610	$ 382,476	$ 181,752
Increase (decrease) in taxes:
Tax-exempt income	(33,799)	(32,466)	(31,071)
State and city income taxes, net of federal income tax effect	34,557	38,360	12,503
Low income housing credits	(40,763)	(29,882)	(20,749)
Non-taxable gain on acquisition	(22,725)
Other	(759)	(1,860)	(3,035)
Income taxes	$ 365,121	$ 356,628	$ 139,400

Non-taxable gain on acquisition.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The sum of other amounts reflected in the reconciliation of the statutory tax provision (benefit) to the actual tax provision (benefit).

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to state and local income tax expense or benefit.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to tax credits.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to income that is exempt from income taxes under enacted tax laws.

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