v3.7.0.1

Debt - Additional Information - Registered Notes (Detail) - MPG Holdco I Inc. [Member] - Registered Notes [Member] - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Oct. 20, 2014
Debt Instrument [Line Items] |  |
Debt Instrument, Face Amount |  | $ 600,000,000
Maturity Year | 2022 |
Interest Rate, Stated Percentage | 7.375% |
Frequency of Periodic Payment | semi-annually on April 15 and October 15 |
Maximum |  |
Debt Instrument [Line Items] |  |
Dividends payable | $ 30,000,000 |
Debt instruments, covenants dividend restriction as percentage of cash proceeds from public offering common stock | 6.00% |

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