Employee Benefit Plans (Details 5) - Pension Benefits - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Dec. 31, 2015	Mar. 31, 2015
Change in plan assets
Fair value of plan assets at beginning of year	$ 2,348,795	$ 2,426,013
Fair value of plan assets at end of year	2,189,900	2,348,795
Significant Unobservable Inputs (Level 3)
Change in plan assets
Fair value of plan assets at beginning of year	698,508
Fair value of plan assets at end of year	710,389	698,508
Common Stock
Change in plan assets
Fair value of plan assets at end of year	95,770
Corporate Debt Securities
Change in plan assets
Fair value of plan assets at end of year	405,993
Corporate Debt Securities \| Significant Unobservable Inputs (Level 3)
Change in plan assets
Fair value of plan assets at beginning of year	187	199
Realized (losses) gains	1	0
Net unrealized (losses) gains	1	1
Net purchases, issuances and settlements	(94)	(13)
Net transfers into (out of) Level 3	0	0
Fair value of plan assets at end of year	95	187
Value of funds in insurance company accounts
Change in plan assets
Fair value of plan assets at end of year	41,238
Value of funds in insurance company accounts \| Significant Unobservable Inputs (Level 3)
Change in plan assets
Fair value of plan assets at beginning of year	1,076	1,131
Realized (losses) gains	16	6
Net unrealized (losses) gains	(7)	(2)
Net purchases, issuances and settlements	(42)	(59)
Net transfers into (out of) Level 3	0	0
Fair value of plan assets at end of year	1,043	1,076
Partnership or joint venture interest
Change in plan assets
Fair value of plan assets at end of year	709,251
Partnership or joint venture interest \| Significant Unobservable Inputs (Level 3)
Change in plan assets
Fair value of plan assets at beginning of year	746,305	689,073
Realized (losses) gains	24,088	38,614
Net unrealized (losses) gains	(37,868)	(5,558)
Net purchases, issuances and settlements	(23,274)	24,176
Net transfers into (out of) Level 3	0	0
Fair value of plan assets at end of year	$ 709,251	$ 746,305

Actual return on plan assets, separately identifying the amount related to assets sold during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=58740216&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 5
-Subparagraph (c)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e2446-114920

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- Definition

Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ 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=49178875&loc=d3e12355-114930

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of increase (decrease) in plan assets from purchases, sales and settlement of plan obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
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- Definition

Transfers in and out of Level 3. For example, transfers due to changes in the observability of significant inputs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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