Revenue - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue by Geographic Area [Line Items]
Revenues	$ 439,743	$ 427,216	$ 497,647	$ 1,403,627	$ 1,487,314
Africa [Member]
Revenue by Geographic Area [Line Items]
Revenues	43,077	51,649	73,901	158,143	222,397
United Kingdom [Member]
Revenue by Geographic Area [Line Items]
Revenues	68,568	62,426	61,914	191,781	180,270
Norway [Member]
Revenue by Geographic Area [Line Items]
Revenues	57,138	45,423	59,875	154,745	162,593
Asia Pacific [Member]
Revenue by Geographic Area [Line Items]
Revenues	30,715	37,122	42,662	113,517	127,211
Brazil [Member]
Revenue by Geographic Area [Line Items]
Revenues	19,296	19,117	25,404	64,902	66,825
Other Geographical [Member]
Revenue by Geographic Area [Line Items]
Revenues	22,071	22,625	14,178	69,355	63,734
Non-US [Member]
Revenue by Geographic Area [Line Items]
Revenues	240,865	238,362	277,934	752,443	823,030
UNITED STATES
Revenue by Geographic Area [Line Items]
Revenues	$ 198,878	$ 188,854	$ 219,713	$ 651,184	$ 664,284