Shareholders' Equity - Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2015 USD ($)
Dividends on common stock [Abstract]
Dividend potential for next fiscal year	$ 114.3
Period for which retained net income considered for approval	2 years

This line item represents the period for which retained net income considered for approval by TNB's regulators is required.

No definition available.

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