Fair Value Measurements - Marketable Securities and Deferred Compensation Fund Investment Assets (Details) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | $ 72,358 | $ 69,496 |
Deferred compensation fund | 25,659 | 25,391 |
Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 21,133 | 21,495 |
Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,526 | 3,896 |
Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 25,659 | 25,391 |
Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 25,659 | 25,391 |
Municipal bonds — available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | 72,358 | 69,496 |
Municipal bonds — available for sale | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | 0 | 0 |
Municipal bonds — available for sale | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | 72,358 | 69,496 |
Municipal bonds — available for sale | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | 0 | 0 |
Municipal bonds — available for sale | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | 72,358 | 69,496 |
Municipal bonds — available for sale | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Marketable securities | 72,358 | 69,496 |
Money Market | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Money Market | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,526 | 3,896 |
Money Market | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Money Market | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,526 | 3,896 |
Money Market | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,526 | 3,896 |
Balanced and Lifestyle | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 9,151 | 9,136 |
Balanced and Lifestyle | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Balanced and Lifestyle | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Balanced and Lifestyle | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 9,151 | 9,136 |
Balanced and Lifestyle | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 9,151 | 9,136 |
Large Cap Growth | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,884 | 5,218 |
Large Cap Growth | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Large Cap Growth | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Large Cap Growth | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,884 | 5,218 |
Large Cap Growth | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 4,884 | 5,218 |
Small Cap Growth | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 2,184 | 2,275 |
Small Cap Growth | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Small Cap Growth | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Small Cap Growth | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 2,184 | 2,275 |
Small Cap Growth | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 2,184 | 2,275 |
Fixed Income | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 2,688 | 2,624 |
Fixed Income | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Fixed Income | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Fixed Income | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 2,688 | 2,624 |
Fixed Income | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 2,688 | 2,624 |
International | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 999 | 1,025 |
International | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
International | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
International | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 999 | 1,025 |
International | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 999 | 1,025 |
Mid Cap Growth | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 1,227 | 1,217 |
Mid Cap Growth | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Mid Cap Growth | Significant Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 0 | 0 |
Mid Cap Growth | Carrying Amount | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | 1,227 | 1,217 |
Mid Cap Growth | Total Fair Value | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Deferred compensation fund | $ 1,227 | $ 1,217 |