Revenue - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue by Geographic Area [Line Items]
Revenues	$ 427,216	$ 536,668	$ 495,781	$ 963,884	$ 989,667
Africa [Member]
Revenue by Geographic Area [Line Items]
Revenues	51,649	63,417	61,390	115,066	148,496
United Kingdom [Member]
Revenue by Geographic Area [Line Items]
Revenues	62,426	60,787	65,058	123,213	118,356
Norway [Member]
Revenue by Geographic Area [Line Items]
Revenues	45,423	52,184	60,252	97,607	102,718
Asia Pacific [Member]
Revenue by Geographic Area [Line Items]
Revenues	37,122	45,680	43,123	82,802	84,549
Brazil [Member]
Revenue by Geographic Area [Line Items]
Revenues	19,117	26,489	23,658	45,606	41,421
Other Geographical [Member]
Revenue by Geographic Area [Line Items]
Revenues	22,625	24,659	28,334	47,284	49,556
Non-US [Member]
Revenue by Geographic Area [Line Items]
Revenues	238,362	273,216	281,815	511,578	545,096
UNITED STATES
Revenue by Geographic Area [Line Items]
Revenues	$ 188,854	$ 263,452	$ 213,966	$ 452,306	$ 444,571