Retirement Benefits - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) employee	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation for all defined benefit pension plans	$ 176,700	$ 176,700	$ 150,400
Percentage of excess gains and losses over benefit obligation or market value of assets amortized		10.00%
Costs of defined contribution plans		$ 10,100	10,300	$ 9,100
Number of participants covering under multi employer pension plan | employee		381
Costs of bargaining unit-sponsored multi-employer plans and defined contribution plans		$ 1,300	1,000	1,000
Weighted average annual rate of increase in the per capita cost of covered health care benefits assumed		6.58%
Assumed decrease of weighted average health care cost trend rate		4.50%
Year that reaches assumed decrease of weighted average health care cost trend rate	2037	2037
Increase in service and interest cost components of the net periodic benefit cost, as 1% increase in health care cost trend rates		$ 200
Increase in accumulated postretirement benefit obligation, as 1% increase in health care cost trend rates		2,100
Decrease in service and interest cost components of the net periodic benefit cost, as 1% decrease in health care cost trend rates		100
Decrease in accumulated postretirement benefit obligation, as 1% decrease in health care cost trend rates		1,800
Future estimated benefit payments for year 2016	$ 14,400	14,400
Future estimated benefit payments for year 2017	10,600	10,600
Future estimated benefit payments for year 2018	10,300	10,300
Future estimated benefit payments for year 2019	10,800	10,800
Future estimated benefit payments for year 2020	10,600	10,600
Future estimated benefit payments for years 2021 to 2025	52,100	52,100
Defined Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, expected contribution for next fiscal year		10,000
401k
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, expected contribution for next fiscal year		8,400
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Settlements		11,000
Settlement loss recognized	$ 3,500	(3,339)	$ 0	$ 0
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected contribution for next fiscal year		5,800
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected contribution for next fiscal year		$ 100
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities, minimum		40.00%
Target allocation of fund assets in equities, maximum		60.00%
Target allocation of fund assets in equities		44.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities, minimum		40.00%
Target allocation of fund assets in equities, maximum		60.00%
Target allocation of fund assets in equities		56.00%