Basis of Presentation and Significant Accounting Policies - Cumulative Effect of the Changes from Adoption of Topic 606 (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	$ 249,846	$ 241,029	$ 232,027
Other assets	525,961	421,328	241,750
Other current liabilities	142,312	143,699	159,914
Other liabilities	633,450	598,659	661,710
Accumulated other comprehensive loss	(877,994)	(787,119)	(785,189)
Retained earnings	655,101	522,465	$ 252,689
ASU 2014-09 [Member] | Difference between revenue guidance in effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other current assets	(9,675)	9,002
Other assets	(183,843)	179,578
Other current liabilities	15,588	(16,215)
Other liabilities	68,038	(63,051)
Accumulated other comprehensive loss	5,716	(1,930)
Retained earnings	$ (281,291)	$ 269,800