Qualified Employee Benefit Plans - Additional Information (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) investment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution expense for foreign entities	$ 7,900,000	$ 7,300,000	$ 6,000,000
Other comprehensive (loss) gain	2,207,000	(24,555,000)	28,190,000
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions to qualified profit sharing plan	14,200,000	13,500,000	12,800,000
Other comprehensive (loss) gain	1,888,000	(20,571,000)	22,436,000
Discount rate and lump sum interest rates	5,600,000	12,000,000	16,100,000
Mortality assumption	1,400,000	7,500,000
Earnings of plan assets exceeding expectations	$ (5,300,000)		$ (6,200,000)
Defined benefit plan, amortization period	36 years
Defined benefit plan, future amortization of prior service cost	$ 23,416
Defined benefit plan, loss to be amortized over next fiscal year	936,295
Accumulated benefit obligation	$ 107,800,000	$ 113,700,000
Assumptions used calculating benefit obligation, discount rate, percent	4.75%	4.30%
Expected long-term rate of return on plan assets	7.00%	7.50%	7.50%
Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Other comprehensive (loss) gain	$ 1,888,000
Dynamic Asset Allocation [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range minimum, percent	18.00%
Target plan asset allocations, percent	28.00%
Target plan asset allocations range maximum, percent	38.00%
Diversifying Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range minimum, percent	0.00%
Target plan asset allocations, percent	17.00%
Target plan asset allocations range maximum, percent	25.00%
Risk Mitigating Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range minimum, percent	10.00%
Target plan asset allocations, percent	15.00%
Target plan asset allocations range maximum, percent	30.00%
Return Seeking Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range minimum, percent	30.00%
Target plan asset allocations, percent	40.00%
Target plan asset allocations range maximum, percent	60.00%
Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Retirement plan, number of investments | investment	2
Private Investment Trusts Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Retirement plan, number of investments | investment	2