Qualified Employee Benefit Plans - Reconciliation of Amounts Recognized in Other Comprehensive Income for the Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	$ (3,043)	$ 3,267	$ (19,656)
Amortization of prior service cost	93	(895)	(5,197)
Changes in employee benefit related items	(2,950)	2,372	(24,853)
Income tax (expense) benefit	(22)	(165)	298
Employee benefit related items, net of tax	(2,972)	$ 2,207	$ (24,555)
Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	(3,115)
Amortization of prior service cost	93
Changes in employee benefit related items	(3,022)
Income tax (expense) benefit	(10)
Employee benefit related items, net of tax	(3,032)
Retired Individual Plan
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	22
Amortization of prior service cost	0
Changes in employee benefit related items	22
Income tax (expense) benefit	(1)
Employee benefit related items, net of tax	21
Foreign Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	50
Amortization of prior service cost	0
Changes in employee benefit related items	50
Income tax (expense) benefit	(11)
Employee benefit related items, net of tax	$ 39