Financial Instruments and Fair Value Disclosures (Tables)

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Abstract]

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

Assets and liabilities measured at fair value are summarized below.

	September 30, 2017
	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Assets at Fair Value		Total Losses for Nine Months Ended
	(In thousands)
Recurring fair value measurements:
Assets:
Short-term investments	$	262,887	$	—	$	—	$	262,887
Mortgage-backed securities		—		4		—		4
Total assets	$	262,887	$	4	$	—	$	262,891
Nonrecurring fair value measurements:
Assets:
Impaired assets (1)	$	—	$	—	$	2,000	$	2,000	$	71,268

(1) Represents the total book value as of September 30, 2017 of one ultra-deepwater rig and one deepwater semisubmersible rig, which were written down to their estimated recoverable amounts during the second quarter of 2017 and were reported as “Drilling and other property and equipment, net of accumulated depreciation,” in our Condensed Consolidated Balance Sheets at September 30, 2017.

	December 31, 2016
	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Assets at Fair Value		Total Losses for Year Ended (1)
	(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)	$	—	$	—	$	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 certain impaired rigs, respectively.

(2) Represents the total book value as of December 31, 2016 for 11 drilling rigs ($45.5 million) and for rig spare parts and supplies ($23.6 million), which were previously written down to their estimated recoverable amounts. 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 Condensed Consolidated Balance Sheets at December 31, 2016.

Fair Values and Related Carrying Values of Our Debt Instruments

	September 30, 2017				December 31, 2016
	Fair Value		Carrying Value		Fair Value		Carrying Value
	(In millions)
5.875% Senior Notes due 2019	$	—	$	—	$	518.6	$	499.8
3.45% Senior Notes due 2023		225.0		249.3		215.0		249.3
7.875% Senior Notes due 2025		528.8		496.4		—		—
5.70% Senior Notes due 2039		411.3		497.1		392.5		497.1
4.875% Senior Notes due 2043		562.5		748.9		532.7		748.9