Retirement Benefits - Net Periodic Pension Expense for Defined Benefit Pension Plans (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit U.S. Pension Plan
Net periodic pension expense for defined benefit pension plans
Service cost	$ 6,800	$ 3,800	$ 6,453
Interest cost	16,116	31,675	29,100
Expected return on assets	(19,711)	(30,105)	(30,975)
Amortization of prior service cost (credits)	867	750	103
Recognized net actuarial loss	9,714	4,435	6,039
Loss on settlement/(gain on curtailment)	250,946		(309)
Net periodic pension expense	264,732	10,555	10,411
Defined Benefit Non-U.S. Pension Plans
Net periodic pension expense for defined benefit pension plans
Service cost	20,517	16,217	15,390
Interest cost	26,511	34,536	32,176
Expected return on assets	(49,066)	(48,077)	(46,420)
Amortization of prior service cost (credits)	(814)
Recognized net actuarial loss	7,681	7,738	6,788
Loss on settlement/(gain on curtailment)	390
Net periodic pension expense	$ 5,219	$ 10,414	$ 7,934