Employee Benefits (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended			120 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of employee gross pay	4.00%
Defined contribution plan, employer matching contributions	$ 2,300	$ 1,800	$ 1,800
Other incentive-based compensation expense	16,000	14,300	$ 13,800
Deferred compensation plan, accrued liability	10,800	8,600
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded (unfunded) status at end of period	2,836	(1,840)
Accumulated benefit obligation	65,800	60,300
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	(23)
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	$ 1,100
Fair value of equity securities, maximum percentage held by a single issuer	10.00%
Estimated future employer contributions in next fiscal year	$ 3,000
Qualified Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, minimum	50.00%
Target plan asset allocation, investment ranges, maximum	70.00%
Qualified Pension Plan [Member] | Small-Cap Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, maximum	20.00%
Qualified Pension Plan [Member] | Mid-Cap Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, maximum	20.00%
Qualified Pension Plan [Member] | International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, maximum	30.00%
Qualified Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, minimum	30.00%
Target plan asset allocation, investment ranges, maximum	50.00%
Qualified Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, minimum	0.00%
Target plan asset allocation, investment ranges, maximum	10.00%
Qualified Pension Plan [Member] | High Yield Bond [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocation, investment ranges, maximum	10.00%
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Available-for-sale securities and other short-term investments, rabbi trusts	$ 11,700	12,300
Funded (unfunded) status at end of period	(13,154)	(13,015)
Accumulated benefit obligation	12,000	$ 11,700
Estimated amortization of prior service cost (credit) from accumulated other comprehensive loss into net period benefit cost, next year	(1)
Estimated amortization of (gain) loss from accumulated other comprehensive loss into net period benefit cost, next year	261
Estimated future employer contributions in next fiscal year	$ 779
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Transition Period Pension Plan Amendment				10 years