Description Of The Business And Summary Of Significant Accounting Policies Description Of The Business And Summary Of Significant Accounting Policies (Reconciliation Of Net Income Attributable To Ensco Shares Used In Basic And Diluted EPS Computations) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Income (loss) from continuing operations attributable to Ensco	$ (304.7)	$ 882.1	$ (1,466.1)
Income from continuing operations allocated to non-vested share awards	(0.4)	(16.6)	(2.0)
Income (loss) from continuing operations attributable to Ensco shares	$ (305.1)	$ 865.5	$ (1,468.1)

Description Of The Business And Summary Of Significant Accounting Policies Description Of The Business And Summary Of Significant Accounting Policies (Reconciliation Of Net Income Attributable To Ensco Shares Used In Basic And Diluted EPS Computations) (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Accounting Policies [Abstract]

Income (loss) from continuing operations attributable to Ensco

$ (304.7)

$ 882.1

$ (1,466.1)

Income from continuing operations allocated to non-vested share awards

(0.4)

(16.6)

(2.0)

Income (loss) from continuing operations attributable to Ensco shares

$ (305.1)

$ 865.5

$ (1,468.1)