Description of Business and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Estimated Useful Lives of Property and Equipment

The estimated useful lives, in years, are shown below:

		Useful Lives
Drilling rigs and other equipment		1.25-15
Buildings		15-20
Other		3-12

Calculation of Basic and Diluted Net Income (Loss) per Share

The following table presents information necessary to calculate net income (loss) per share for the years ended December 31, 2015, 2014 and 2013, as well as potentially dilutive securities excluded from the weighted average number of diluted common shares outstanding because their inclusion would have been anti-dilutive (in thousands, except per share amounts):

	2015			2014			2013
BASIC EPS:
Net income (loss)	$	(294,486	)	$	162,664		$	188,009
Adjust for (income) loss attributed to holders of non-vested restricted stock		3,022			(1,663	)		(1,859	)
Income (loss) attributed to common stockholders	$	(291,464	)	$	161,001		$	186,150

Weighted average number of common shares outstanding, excluding non-vested shares of restricted stock		145,416			144,066			144,356

Basic net income (loss) per common share	$	(2.00	)	$	1.12		$	1.29

DILUTED EPS:
Income (loss) attributed to common stockholders	$	(291,464	)	$	161,001		$	186,150

Weighted average number of common shares outstanding, excluding non-vested shares of restricted stock		145,416			144,066			144,356
Add dilutive effect of potential common shares		—			1,310			947
Weighted average number of diluted common shares outstanding		145,416			145,376			145,303

Diluted net income (loss) per common share	$	(2.00	)	$	1.11		$	1.28

Potentially dilutive securities excluded as anti-dilutive		7,781			1,088			2,447