Subsequent Events	12 Months Ended
Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	26. Subsequent Events Variation Margin as Settlement Effective January 3, 2017, the Chicago Mercantile Exchange (“CME”), a clearing organization, amended its rulebook to legally characterize variation margin cash payments for cleared over-the-counter derivatives as settlement rather than collateral. As a result, variation margin payments are considered a single unit of account with the associated derivative for accounting and disclosure purposes. We currently clear a significant portion of our derivative trades through the CME. At December 31, 2016, and in all prior periods presented, we did not offset cash collateral held from or posted to the CME with the associated derivative asset or liability on our balance sheet. Further information regarding our treatment of cash collateral exchanged with clearing organizations is provided in Note 9 (“Derivatives and Hedging Activities”). In future periods, the variation margin cash payments posted and held in relation to CME-cleared derivative assets and liabilities will be applied against the gross balances of those associated derivative assets and liabilities. These rulebook amendments are expected to significantly reduce the carrying value of derivative assets and liabilities presented on our Consolidated Balance Sheets. The changes to the rulebook are not expected to impact the hedge accounting relationships involving CME-cleared derivatives, and they are expected to have an immaterial effect on our results of operations. Redemption of Series C Preferred Stock On January 12, 2017, we provided notice of our intention to redeem all outstanding shares of the Series C Preferred Stock on February 15, 2017. On February 15, 2017, the Series C Preferred Stock was redeemed for cash at a redemption price of $25 per share. The redemption date was also a dividend payment date, and declared dividends of $0.539063 per share were also paid separately on February 15, 2017. The Series C Preferred Stock was initially issued in connection with the First Niagara acquisition to replace First Niagara’s outstanding preferred stock. For additional information on the Series C Preferred Stock, see Note 23 (“Shareholders' Equity”).

26. Subsequent Events

Variation Margin as Settlement

Effective January 3, 2017, the Chicago Mercantile Exchange (“CME”), a clearing organization, amended its rulebook to legally characterize variation margin cash payments for cleared over-the-counter derivatives as settlement rather than collateral. As a result, variation margin payments are considered a single unit of account with the associated derivative for accounting and disclosure purposes. We currently clear a significant portion of our derivative trades through the CME. At December 31, 2016, and in all prior periods presented, we did not offset cash collateral held from or posted to the CME with the associated derivative asset or liability on our balance sheet. Further information regarding our treatment of cash collateral exchanged with clearing organizations is provided in Note 9 (“Derivatives and Hedging Activities”). In future periods, the variation margin cash payments posted and held in relation to CME-cleared derivative assets and liabilities will be applied against the gross balances of those associated derivative assets and liabilities. These rulebook amendments are expected to significantly reduce the carrying value of derivative assets and liabilities presented on our Consolidated Balance Sheets.

The changes to the rulebook are not expected to impact the hedge accounting relationships involving CME-cleared derivatives, and they are expected to have an immaterial effect on our results of operations.

Redemption of Series C Preferred Stock

On January 12, 2017, we provided notice of our intention to redeem all outstanding shares of the Series C Preferred Stock on February 15, 2017. On February 15, 2017, the Series C Preferred Stock was redeemed for cash at a redemption price of $25 per share. The redemption date was also a dividend payment date, and declared dividends of $0.539063 per share were also paid separately on February 15, 2017. The Series C Preferred Stock was initially issued in connection with the First Niagara acquisition to replace First Niagara’s outstanding preferred stock. For additional information on the Series C Preferred Stock, see Note 23 (“Shareholders' Equity”).