Segments and Geographic Area Analysis (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Revenues from contract drilling services by equipment-type
Contract drilling	$ 755,155	$ 788,873
Revenues related to reimbursable expenses	13,487	17,516
Total revenues	768,642	806,389
Ultra Deepwater [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	244,589	198,730
Deepwater [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	146,003	132,252
Mid Water [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	318,595	409,583
Total Floaters [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	709,187	740,565
Jack-ups [Member]
Revenues from contract drilling services by equipment-type
Contract drilling	45,968	48,218
Other [Member]
Revenues from contract drilling services by equipment-type
Contract drilling		$ 90