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, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	$ 3,267	$ (19,656)	$ 22,853
Amortization of prior service cost	(895)	(5,197)	5,828
Changes in employee benefit related items	2,372	(24,853)	28,634
Income tax (expense) benefit	(165)	298	(444)
Employee benefit related items, net of tax	2,207	$ (24,555)	$ 28,190
Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	2,882
Amortization of prior service cost	(895)
Changes in employee benefit related items	1,987
Income tax (expense) benefit	(99)
Employee benefit related items, net of tax	1,888
Retired Individual Plan
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	96
Amortization of prior service cost	0
Changes in employee benefit related items	96
Income tax (expense) benefit	(2)
Employee benefit related items, net of tax	94
Foreign Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Recognized actuarial (loss) gain	289
Amortization of prior service cost	0
Changes in employee benefit related items	289
Income tax (expense) benefit	(64)
Employee benefit related items, net of tax	$ 225