Senior Notes - Summary of Carrying Value of Outstanding Senior Notes, Net of Unamortized Discount and Debt Issuance Costs (Detail) $ in Thousands	Sep. 30, 2017 USD ($)
Debt Instrument [Line Items]
Senior Notes	$ 1,971,852
3.45% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Senior Notes	248,090
7.875% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Senior Notes	489,200
5.70% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Senior Notes	492,930
4.875% Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Senior Notes	$ 741,632

Including the current and noncurrent portions, carrying value as of the balance sheet date of notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), net of unamortized discount and debt issuance costs. Senior note holders are paid off in full before any payments are made to junior note holders.

No definition available.

Name:	do_SeniorNotesNet
Namespace Prefix:	do_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant