Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Operating revenues	$ 771,406	$ 761,920	$ 1,571,046	$ 1,496,114
U.S. Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	323,402	264,395	643,611	505,397
Canada Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	11,389	17,442	36,704	49,329
International Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	326,905	377,986	664,161	746,831
Drilling Solutions
Disaggregation of Revenue [Line Items]
Operating revenues	64,583	59,859	130,005	122,507
Rig Technologies
Disaggregation of Revenue [Line Items]
Operating revenues	72,751	81,321	144,504	145,990
Other
Disaggregation of Revenue [Line Items]
Operating revenues	(27,624)	(39,083)	(47,939)	(73,940)
Operating segment | Lower 48
Disaggregation of Revenue [Line Items]
Operating revenues	365,599	318,380	723,258	617,842
Operating segment | Offshore Gulf Of Mexico [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	41,492	34,874	87,218	59,164
Operating segment | ALASKA
Disaggregation of Revenue [Line Items]
Operating revenues	17,052	14,027	38,939	30,148
Operating segment | Canada Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	14,193	29,089	42,809	66,656
Operating segment | Middle East And Asia [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	207,762	256,018	416,836	502,811
Operating segment | Latin America [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	92,680	93,393	189,198	182,917
Operating segment | Europe Africa And CIS [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	60,252	55,222	120,727	110,516
Operating segment | U.S. Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	323,402	264,395	643,611	505,397
Operating segment | U.S. Drilling | Lower 48
Disaggregation of Revenue [Line Items]
Operating revenues	268,788	219,389	527,659	423,981
Operating segment | U.S. Drilling | Offshore Gulf Of Mexico [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	38,727	32,064	80,208	53,055
Operating segment | U.S. Drilling | ALASKA
Disaggregation of Revenue [Line Items]
Operating revenues	15,887	12,942	35,744	28,361
Operating segment | Canada Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	11,389	17,442	36,704	49,329
Operating segment | Canada Drilling | Canada Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	11,389	17,442	36,704	49,329
Operating segment | International Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	326,905	377,986	664,161	746,831
Operating segment | International Drilling | Middle East And Asia [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	185,077	240,508	373,045	474,367
Operating segment | International Drilling | Latin America [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	88,792	87,809	181,159	171,691
Operating segment | International Drilling | Europe Africa And CIS [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	53,036	49,669	109,957	100,773
Operating segment | Drilling Solutions
Disaggregation of Revenue [Line Items]
Operating revenues	64,583	59,859	130,005	122,507
Operating segment | Drilling Solutions | Lower 48
Disaggregation of Revenue [Line Items]
Operating revenues	46,649	41,418	90,697	85,687
Operating segment | Drilling Solutions | Offshore Gulf Of Mexico [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	2,765	2,810	7,010	6,109
Operating segment | Drilling Solutions | ALASKA
Disaggregation of Revenue [Line Items]
Operating revenues	921	877	2,649	1,443
Operating segment | Drilling Solutions | Canada Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	382	1,425	1,056	3,716
Operating segment | Drilling Solutions | Middle East And Asia [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	9,422	9,007	19,929	16,735
Operating segment | Drilling Solutions | Latin America [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	3,426	3,665	6,657	7,649
Operating segment | Drilling Solutions | Europe Africa And CIS [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	1,018	657	2,007	1,168
Operating segment | Rig Technologies
Disaggregation of Revenue [Line Items]
Operating revenues	72,751	81,321	144,504	145,990
Operating segment | Rig Technologies | Lower 48
Disaggregation of Revenue [Line Items]
Operating revenues	50,162	57,573	104,902	108,174
Operating segment | Rig Technologies | ALASKA
Disaggregation of Revenue [Line Items]
Operating revenues	244	208	546	344
Operating segment | Rig Technologies | Canada Drilling
Disaggregation of Revenue [Line Items]
Operating revenues	2,422	10,222	5,049	13,611
Operating segment | Rig Technologies | Middle East And Asia [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	13,263	6,503	23,862	11,709
Operating segment | Rig Technologies | Latin America [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	462	1,919	1,382	3,577
Operating segment | Rig Technologies | Europe Africa And CIS [Member]
Disaggregation of Revenue [Line Items]
Operating revenues	6,198	4,896	8,763	8,575
Other reconciling items (1) | Other
Disaggregation of Revenue [Line Items]
Operating revenues	(27,624)	(39,083)	(47,939)	(73,940)
Other reconciling items (1) | Other | Other
Disaggregation of Revenue [Line Items]
Operating revenues	(27,624)	(39,083)	(47,939)	(73,940)
Other reconciling items (3)
Disaggregation of Revenue [Line Items]
Operating revenues	$ 27,624	$ 39,083	$ 47,939	$ 73,940