Goodwill by Operating Segment (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Goodwill [Line Items]
Balance at beginning of period	$ 410,756
Changes to goodwill	2,104
Balance at end of period	412,860
Contract Drilling
Goodwill [Line Items]
Balance at beginning of period	395,060
Balance at end of period	395,060
Other Operations
Goodwill [Line Items]
Balance at beginning of period	15,696
Changes to goodwill	2,104
Balance at end of period	$ 17,800