Dividends Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
Feb. 28, 2018	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016
Payments of Ordinary Dividends, Common Stock	$ 654.9	$ 395.4
Dividends payable			$ 655.1	$ 395.4
Annual variable dividend [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 1.1247	$ 0.6808

Aggregate dividends paid during the period for each share of common stock outstanding.

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Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

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