Segments and Geographic Area Analysis (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues from contract drilling services by equipment-type
Contract drilling	$ 726,261	$ 869,646	$ 1,481,416	$ 1,658,519
Revenues related to reimbursable expenses	11,927	19,850	25,414	37,366
Total revenues	738,188	889,496	1,506,830	1,695,885
Ultra-Deepwater [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	233,071	233,271	477,660	432,001
Deepwater [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	142,565	192,791	288,568	325,043
Mid-Water [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	310,462	383,067	629,057	792,650
Total Floaters [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	686,098	809,129	1,395,285	1,549,694
Jack-ups [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	40,163	60,512	86,131	108,730
Other [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	$ 0	$ 5	$ 0	$ 95