Trading Securities (Details) - USD ($) $ in Thousands  | 
Jun. 30, 2018  | 
Mar. 31, 2018  | 
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|---|---|---|---|---|
| Trading securities | $ 184,350 | |||
| (Recast) | ||||
| Trading securities | [1] | $ 212,595 | ||
| Equity securities | ||||
| Trading securities | 146,487 | |||
| Equity securities | (Recast) | ||||
| Trading securities | 177,339 | |||
| Debt securities | ||||
| Trading securities | 37,615 | |||
| Debt securities | (Recast) | ||||
| Trading securities | 34,986 | |||
| Mutual investment funds | ||||
| Trading securities | $ 248 | |||
| Mutual investment funds | (Recast) | ||||
| Trading securities | $ 270 | |||
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- Definition Amount of investment in marketable security. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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