Financial Instruments and Fair Value Disclosures (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis

December 31, 2016
	Fair Value Measurements Using						Assets at Fair Value		Total  Losses for Year Ended (1)
	Level 1		Level 2		Level 3
	(In thousands)
Recurring fair value measurements:
Assets:
Short-term investments	$	146,360	$	—	$	—	$	146,360
Mortgage-backed securities		—		35		—		35
Total assets	$	146,360	$	35	$	—	$	146,395
Nonrecurring fair value measurements:
Assets:
Impaired assets (2)(3)	$	—	$	—	$	69,153	$	69,153	$	678,145

(1) Represents impairment losses of $8.1 million and $670.0 million recognized during the year ended December 31, 2016 related to our rig spare parts and supplies and 2016 Impaired Rigs, respectively. See Notes 2 and 3.

(2) Represents the total book value as of December 31, 2016 for 11 drilling rigs ($45.5 million), which were written down to their estimated recoverable amounts in 2015 and 2016, and for rig spare parts and supplies ($23.6 million), which were written down to their estimated recoverable amounts in the second quarter of 2016. Of the total fair value, $23.6 million, $0.4 million and $45.1 million were reported as “Prepaid expenses and other current assets,” “Assets held for sale” and “Drilling and other property and equipment, net of accumulated depreciation,” respectively, in our Consolidated Balance Sheets at December 31, 2016. See Notes 1, 2 and 3.

(3) Includes depreciation expense of $23.9 million recognized during the year ended December 31, 2016 for rigs which have previously been written down to their estimated fair values using an income approach. Also excludes four jack-up rigs, three mid-water semisubmersible rigs and one deepwater semisubmersible rig with an aggregate fair value of $16.0 million, which have been sold.

	December 31, 2015
	Fair Value Measurements Using						Assets at Fair Value		Total  Losses for Year Ended (1)
	Level 1		Level 2		Level 3
	(In thousands)
Recurring fair value measurements:
Assets:
Short-term investments	$	105,659	$	—	$	—	$	105,659
Corporate bonds		—		11,438		—		11,438
Mortgage-backed securities		—		80		—		80
Total assets	$	105,659	$	11,518	$	—	$	117,177
Nonrecurring fair value measurements:
Assets:
Impaired assets (2)(3)	$	—	$	—	$	189,600	$	189,600	$	860,441

(1) Represents the aggregate impairment loss recognized for the year ended December 31, 2015 related to our 2015 Impaired Rigs.

(2) Represents the book value of our 2015 Impaired Rigs, which were written down to their estimated recoverable amounts during 2015, of which $14.2 million and $175.4 million were reported as “Assets held for sale” and “Drilling and other property and equipment, net of accumulated depreciation,” respectively, in our Consolidated Balance Sheets at December 31, 2015.

(3) Excludes five rigs with an aggregate fair value of $2.4 million, which were impaired in 2015, but were subsequently sold for scrap during the year.

Fair Values and Related Carrying Values of Our Debt Instruments

	December 31, 2016				December 31, 2015
	Fair Value		Carrying Value		Fair Value		Carrying Value
	(In millions)
5.875% Senior Notes due 2019	$	518.6	$	499.8	$	506.8	$	499.7
3.45% Senior Notes due 2023		215.0		249.3		208.0		249.2
5.70% Senior Notes due 2039		392.5		497.1		360.0		497.0
4.875% Senior Notes due 2043		532.7		748.9		455.3		748.9