Revenue from Contracts with Customers (Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Total assets	$ 5,972,903		$ 6,687,420	$ 5,837,133
Accounts receivable, net	455,807		427,022
Other current assets and prepayments	99,332		83,293
Other assets	413,239		540,751
Total Liabilities
Total liabilities	5,733,431		6,498,859
Accounts payable and accrued liabilities	1,401,635		1,458,854
Advance billings	237,529		257,766
Other noncurrent liabilities	474,862		519,079
Stockholders' equity:
Total stockholders’ equity	239,472		188,561	$ (103,660)	$ 178,721
Retained earnings	5,416,777		5,229,584
Accumulated other comprehensive loss	(948,426)		$ (792,173)
ASC 606
Stockholders' equity:
Retained earnings		$ (9,000)
Prior guidance | ASC 606
ASSETS
Total assets	5,951,075
Accounts receivable, net	454,414
Other current assets and prepayments	90,659
Other assets	400,955
Total Liabilities
Total liabilities	5,737,751
Accounts payable and accrued liabilities	1,396,650
Advance billings	252,472
Other noncurrent liabilities	477,208
Stockholders' equity:
Total stockholders’ equity	213,325
Retained earnings	5,389,732
Accumulated other comprehensive loss	(947,528)
Total increase (decrease) | ASC 606
ASSETS
Total assets	21,828
Accounts receivable, net	1,393
Other current assets and prepayments	8,673
Other assets	12,284
Total Liabilities
Total liabilities	(4,320)
Accounts payable and accrued liabilities	4,985
Advance billings	(14,943)
Other noncurrent liabilities	(2,346)
Stockholders' equity:
Total stockholders’ equity	26,147
Retained earnings	27,045
Accumulated other comprehensive loss	$ (898)