Incentive and Deferred Compensation Plans (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Total incentive and deferred compensation plans
Awards, employer match, and hypothetical earnings by plan:
Total plan awards and earnings	$ 22,506	$ 21,534	$ 18,042
Total plan awards paid	(14,317)	(14,839)	(10,602)
Gross incentive plan and deferred compensation liabilities at end of period	37,457	38,978	32,828
Annual incentive plan
Awards, employer match, and hypothetical earnings by plan:
Annual incentive plan awards	7,057	6,222	8,015
Long-term incentive plan
Awards, employer match, and hypothetical earnings by plan:
Long-term incentive plan awards	13,407	12,523	7,941
Deferred compensation plans and stock compensation plan for outside directors
Awards, employer match, and hypothetical earnings by plan:
Deferred compensation plans, employer match, and hypothetical earnings	2,042	2,789	2,086
Compensation deferred under the plans	996	527	146
Distributions from the deferred compensation plans	(1,688)	(1,072)	(823)
Funding of rabbi trust for outside directors	$ (9,018)	$ 0	$ 0