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Defined Benfit Plan (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Mar. 31, 2016 | Dec. 31, 2016
Components of Net Periodic Benefit Cost [Abstract] |  |  |  |  |
Service cost | $ 1,326 |  | $ 1,240 |  |
Interest cost | 1,903 |  | 1,878 |  |
Other cost | 1,038 |  | 1,111 |  |
Expected return on assets | (2,066) |  | (1,895) |  |
Net periodic benefit cost | 2,201 |  | $ 2,334 |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 122,966 |  |  | $ 119,261 |
Employer Contributions [Abstract] |  |  |  |  |
Estimated employer contributions for the current fiscal year | 7,500 |  |  |  |
Defined Contribution Plan, Employer Discretionary Contribution Amount | 0 |  |  |  |
Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 76,233 |  |  | 73,060 |
Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 46,733 |  |  | 46,201 |
Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | $ 0 |  |  | $ 0 |
Equity Securities [Member] |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Target plan asset allocations | 55.00% |  |  | 55.00% |
Fixed Income Securities |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Target plan asset allocations | 45.00% |  |  | 45.00% |
Cash and cash equivalents |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | $ 5,725 |  |  | $ 10,050 |
Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,725 |  |  | 10,050 |
Cash and cash equivalents | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 |  |  | 0 |
Cash and cash equivalents | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 |  |  | 0 |
Actively Managed | All Cap Equity |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,955 | [1] |  | 5,290 | [2]
Actively Managed | All Cap Equity | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,926 | [1] |  | 5,266 | [2]
Actively Managed | All Cap Equity | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 29 | [1] |  | 24 | [2]
Actively Managed | All Cap Equity | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | U.S. Large Cap Equity |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 43,579 | [1] |  | 39,534 | [2]
Actively Managed | U.S. Large Cap Equity | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 43,579 | [1] |  | 39,534 | [2]
Actively Managed | U.S. Large Cap Equity | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | U.S. Large Cap Equity | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | U.S. Mid Cap Equity |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 8,634 | [1] |  | 7,021 | [2]
Actively Managed | U.S. Mid Cap Equity | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 8,634 | [1] |  | 7,021 | [2]
Actively Managed | U.S. Mid Cap Equity | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | U.S. Mid Cap Equity | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | U.S. Small Cap Equity |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 7,256 | [1] |  | 6,357 | [2]
Actively Managed | U.S. Small Cap Equity | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 7,256 | [1] |  | 6,357 | [2]
Actively Managed | U.S. Small Cap Equity | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | U.S. Small Cap Equity | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | Non-U.S. Large Cap Equity |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,113 | [1] |  | 4,832 | [2]
Actively Managed | Non-U.S. Large Cap Equity | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,113 | [1] |  | 4,832 | [2]
Actively Managed | Non-U.S. Large Cap Equity | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets |  | [1] |  | 0 | [2]
Actively Managed | Non-U.S. Large Cap Equity | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets |  | [1] |  | 0 | [2]
Actively Managed | REIT |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,702 | [1] |  | 5,663 | [2]
Actively Managed | REIT | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Actively Managed | REIT | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 5,702 | [1] |  | 5,663 | [2]
Actively Managed | REIT | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [1] |  | 0 | [2]
Fixed Income |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 41,002 | [3] |  | 40,514 | [4]
Fixed Income | Quoted Prices in Active Markets for Identical Assets |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 0 | [3] |  | 0 | [4]
Fixed Income | Significant Observable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | 41,002 | [3] |  | 40,514 | [4]
Fixed Income | Significant Unobservable Inputs |  |  |  |  |
Plan Assets [Abstract] |  |  |  |  |
Fair value of plan assets | $ 0 | [3] |  | $ 0 | [4]
[1] | Actively managed portfolio of securities with the goal to exceed the stated benchmark performance.
[2] | Actively managed portfolio of securities with the goal to exceed the stated benchmark performance.
[3] | Actively managed portfolio of fixed income securities with the goal to exceed the Barclays 1-5 Year Government/Credit, Barclays Intermediate Government/Credit, and Merrill Lynch Preferred Stock Fixed Rate.
[4] | Actively managed portfolio of fixed income securities with the goal to exceed the Barclays 1-5 Year Government/Credit, Barclays Intermediate Government/Credit, and Merrill Lynch Preferred Stock Fixed Rate.

X
- Definition The employer's best estimate of total contributions expected to be paid to the plan for the current fiscal period. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions. + References No definition available. + Details
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- Definition An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Expected Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512171 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 50 -URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12355-114930 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Assets -URI http://asc.fasb.org/extlink&oid=6749337 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Plan Assets -URI http://asc.fasb.org/extlink&oid=6520858 + Details
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- Definition The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Service Cost (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6525008 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Target allocation of investments of this type to total plan assets presented on a weighted average basis. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c)(i) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e2446-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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