Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary Of Non-Vested Share Award Related Compensation Expense Recognized

The following table summarizes share award and cash-settled award compensation expense recognized during each of the years in the three-year period ended December 31, 2017 (in millions):



	2017			2016			2015
Contract drilling	$	18.3		$	19.9		$	19.5
General and administrative	14.5			16.6			17.8
	32.8			36.5			37.3
Tax benefit	(4.8		)	(5.9		)	(4.8		)
Total	$	28.0		$	30.6		$	32.5

Summary Of Value Of Non-Vested Share Awards Granted And Vested

The following table summarizes the value of share awards and cash-settled awards granted and vested during each of the years in the three-year period ended December 31, 2017:



	Share Awards						Cash-Settled Awards
	2017		2016		2015		2017		2016		2015
Weighted-average grant-date fair value of share awards granted (per share)	$	7.90	$	10.42	$	23.95	$	6.27	$	9.64	$	—
Total fair value of share awards vested during the period (in millions)	$	8.6	$	8.8	$	18.0	$	3.9	$	—	$	—

Summary Of Non-Vested Share Award Activity

The following table summarizes share awards and cash-settled awards activity for the year ended December 31, 2017 (shares in thousands):



	Share Awards				Cash-settled Awards
	Awards		Weighted-Average Grant-Date Fair Value		Awards		Weighted-Average Grant-Date Fair Value
Share awards and cash-settled awards as of December 31, 2016	3,073		$	26.02	3,060		$	9.64
Granted	1,433		7.90		4,968		6.27
Vested	(1,123	)	32.75		(614	)	9.64
Forfeited	(78	)	31.52		(325	)	7.77
Share awards and cash-settled awards as of December 31, 2017	3,305		$	16.06	7,089		$	7.37