Employee and Retiree Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended			120 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Pension and Other Postretirement Benefits Disclosure [Line Items]
Future annual rate of increase in cost of health care for 2016 to measure postretirement benefit obligations	7.20%
Ultimate rate of health care cost in 2028 and thereafter	4.50%
Provisions of the March 2010 Health Care Reform	In March 2010, the United States Congress enacted a health care reform law. Along with other provisions, the law (a) eliminated the tax free status of federal subsidies to companies with qualified retiree prescription drug plans that are actuarially equivalent to Medicare Part D plans beginning in 2013; (b) imposes a 40% excise tax on high-cost health plans as defined in the law beginning in 2018; (c) eliminated lifetime or annual coverage limits and required coverage for preventative health services beginning in September 2010; and (d) imposed a fee of $2 (subsequently adjusted for inflation) for each person covered by a health insurance policy beginning in September 2010.
Equity securities minimum market capitalization	$ 100,000,000			$ 100,000,000
Weighted average expected return on plan asset	6.00%
Basis used to determine expected return on plan asset, average expected investment expenses	0.53%
Perentage return on plan assets				5.72%
Defined benefit plan, percentage of employer's matching contribution	6.00%	6.00%	6.00%
Thrift plan expense	$ 7,607,000	$ 10,229,000	$ 13,839,000
Investment 2 [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Domestic plan, investment notice period	90 days
Investment 3 [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Domestic plan, investment lock up period	3 years
Domestic plan, investment notice period	95 days
Foreign Other Postretirement Benefit Plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	$ 31,000
Expected benefit plan contributions to be made during next year	27,000
Domestic postretirement benefits plan [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	3,758,000
Expected benefit plan contributions to be made during next year	5,343,000
Domestic defined benefit pension plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	15,752,000
Expected benefit plan contributions to be made during next year	6,910,000
Foreign Plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to benefit plans	15,690,000
Expected benefit plan contributions to be made during next year	$ 1,555,000
United Kingdom [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Asset performance compared to a benchmark return, percent targeted to outperform the benchmark over three years	0.75%
Percentage fixed income allocation	95.00%			95.00%
Maximum percentage of income investment in securities	5.00%			5.00%
United Kingdom [Member] | Foreign Other Postretirement Benefit Plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Description of equity and fixed income securities allocation	Approximately one-half of the equity allocation is to be invested in U.K. securities and the remainder split between North American, European, Japanese and other Pacific Basin securities. A minimum of 95% of the fixed income allocation is to be invested in U.K. securities with up to 5% in international or high yield bonds.
Maximum [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Investment Manager's portfolio to be held in equity securities of any one issuer	10.00%			10.00%
Equity Securities [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	40.00%
Target allocations of plan assets, maximum	70.00%
Weighted average expected return on plan asset	8.00%
Equity Securities [Member] | United Kingdom [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	27.00%
Target allocations of plan assets, maximum	98.00%
Target allocations of plan assets	60.00%
Equity Securities [Member] | Canada [Member] | Foreign Other Postretirement Benefit Plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	40.00%
Target allocations of plan assets, maximum	75.00%
Target allocations of plan assets	60.00%
Fixed Income Securities [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	30.00%
Target allocations of plan assets, maximum	60.00%
Fixed income portfolio, maximum average maturity years	11 years
Weighted average expected return on plan asset	3.71%
Fixed Income Securities [Member] | United Kingdom [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	25.00%
Target allocations of plan assets, maximum	60.00%
Target allocations of plan assets	40.00%
Fixed Income Securities [Member] | Canada [Member] | Foreign Other Postretirement Benefit Plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	25.00%
Target allocations of plan assets, maximum	45.00%
Target allocations of plan assets	35.00%
US Long/Short Equity Fund [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	0.00%
Target allocations of plan assets, maximum	15.00%
Cash and Equivalents [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	0.00%
Target allocations of plan assets, maximum	15.00%
Cash [Member] | United Kingdom [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, maximum	5.00%
Cash [Member] | Canada [Member] | Foreign Other Postretirement Benefit Plans [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Target allocations of plan assets, minimum	0.00%
Target allocations of plan assets, maximum	15.00%
Target allocations of plan assets	5.00%
Emerging Market Commingled Equity Fund [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Domestic plan, investment notice period	10 days