Income Taxes - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of the applicable statutory U.S. income tax rate to the effective tax rate
Statutory U.S. federal tax rate	35.00%	35.00%	35.00%
Increase/(decrease) in tax rate resulting from:
U.S. state and local income taxes, net of U.S. federal income tax benefit	2.70%	2.20%	1.60%
Tax-exempt income	(3.10%)	(3.10%)	(2.90%)
Non-U.S. subsidiary earnings	(2.00%)	(4.90%)	(2.40%)
Business tax credits	(5.40%)	(5.40%)	(4.20%)
Nondeductible legal expense	2.40%	8.00%	(0.20%)
Other, net	(2.60%)	(1.00%)	(0.50%)
Effective tax rate	27.00%	30.80%	26.40%

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income (loss) exempt from income taxes.

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