Income Taxes - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
	Dec. 22, 2017	Dec. 31, 2017	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Corporate tax rate					3.00%	3.00%	2.00%
Deferred tax benefit relating to tax cuts and jobs act	$ 764,000	$ 6,000
Total provision for income taxes					(1.00%)	29.00%	22.00%
Deferred income tax benefit		764,000			$ 651,000	$ (114,000)	$ 108,000
Income tax expense					25,000	(580,000)	(358,000)
Valuation allowance		126,000		$ 72,000	$ 126,000	$ 122,000	$ 72,000	$ 75,000
Statutory federal income tax rate					35.00%	35.00%	35.00%
Undistributed earnings		4,500,000			$ 4,500,000
Unrecognized tax benefits that would impact effective tax rate		77,000			77,000	$ 76,000
Changes in unrecognized tax benefits		10,000			10,000
Decrease in unrecognized tax benefits		39,000			39,000
Unrecognized tax benefits		115,000		$ 107,000	115,000	112,000	$ 107,000	$ 145,000
Unrecognized tax benefits, interest on income taxes expense					1,000	1,000	$ 12,000
Unrecognized tax benefits, income tax penalties and interest accrued		35,000			35,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		89,000			89,000	59,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		353,000			353,000	293,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		253,000			253,000	$ 116,000
Other Noncurrent Liabilities
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits		69,000			69,000
Unrecognized tax benefits, income tax penalties and interest accrued		25,000			25,000
Other Current Liabilities
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits		47,000			47,000
Unrecognized tax benefits, income tax penalties and interest accrued		$ 10,000			$ 10,000
United Kingdom
Operating Loss Carryforwards [Line Items]
Corporate tax rate				18.00%
United States and United Kingdom
Operating Loss Carryforwards [Line Items]
Total provision for income taxes					30.00%	2.00%	4.00%
Deferred income tax benefit					$ 764,000	$ 34,000	$ 60,000
Maximum | United Kingdom
Operating Loss Carryforwards [Line Items]
Corporate tax rate			18.00%	20.00%
Minimum | United Kingdom
Operating Loss Carryforwards [Line Items]
Corporate tax rate			17.00%	19.00%