Revenue - Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Revenue by Geographic Area [Line Items]
Revenues	$ 536,668	$ 560,810	$ 493,886
Africa [Member]
Revenue by Geographic Area [Line Items]
Revenues	63,417	70,421	87,106
United Kingdom [Member]
Revenue by Geographic Area [Line Items]
Revenues	60,787	76,078	53,298
Norway [Member]
Revenue by Geographic Area [Line Items]
Revenues	52,184	55,169	42,466
Asia Pacific [Member]
Revenue by Geographic Area [Line Items]
Revenues	45,680	47,558	41,426
Brazil [Member]
Revenue by Geographic Area [Line Items]
Revenues	26,489	26,686	17,763
Other Geographical [Member]
Revenue by Geographic Area [Line Items]
Revenues	24,659	27,857	21,222
Non-US [Member]
Revenue by Geographic Area [Line Items]
Revenues	273,216	303,769	263,281
UNITED STATES
Revenue by Geographic Area [Line Items]
Revenues	$ 263,452	$ 257,041	$ 230,605