Long-term debt - New Credit Facilities (Details) CAD in Millions, $ in Millions | May. 02, 2016CAD | May. 02, 2016USD ($) | Apr. 13, 2016CAD | Apr. 13, 2016USD ($) | Jul. 26, 2015USD ($) | Apr. 30, 2016USD ($) | Mar. 31, 2016CAD | Mar. 31, 2016USD ($) | Sep. 30, 2015USD ($) | Sep. 30, 2015USD ($) | Apr. 13, 2016USD ($) | Mar. 31, 2016USD ($) | Dec. 31, 2015USD ($) |
Long-term debt excluding debentures | Senior unsecured notes, due June 2036 (Cdn$210.0) | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | | | 5.95% | | | | | 5.95% | |
Long-term debt excluding debentures | Senior unsecured notes due 2018 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | 9.00% | | | | | | | | |
Aggregate principal amount of debt repurchased | | | | | $ 310.9 | | | | | | | | |
Debt Instrument, Repurchase Amount | | | | | | | | | $ 330.4 | $ 330.4 | | | |
Redemption price percentage of principal amount | | | | | 104.50% | | | | | | | | |
Long-term debt excluding debentures | Senior unsecured notes due 2018 | Interest expense | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Debt Instrument Redemption Applicable Make Whole Premium | | | | | | | | | | 14 | | | |
Accrued interest paid in redemption of debt | | | | | | | | | | 5.5 | | | |
Debt Instrument Write Off of Deferred Financing Cost Related to Repurchase | | | | | | | | | $ 9 | $ 9 | | | |
Convertible Debentures | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | | | | | | | | | | | | $ 271.4 | $ 277.7 |
Convertible Debentures | 6.25% Debentures due March 2017 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | CAD | | | | | | | CAD 67.2 | | | | | | |
Interest rate (as a percent) | | | | | | | 6.25% | | | | | 6.25% | |
Convertible Debentures | 6.25% Debentures due March 2017 | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Proceeds deposited with trustee in advance of payment of certain unsecured subordinated debentures | CAD | | | CAD 67.2 | | | | | | | | | | |
Convertible Debentures | 5.6% Debentures due June 2017 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | CAD | | | | | | | CAD 75.8 | | | | | | |
Interest rate (as a percent) | | | | | | | 5.60% | | | | | 5.60% | |
Convertible Debentures | 5.6% Debentures due June 2017 | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Proceeds deposited with trustee in advance of payment of certain unsecured subordinated debentures | CAD | | | CAD 75.8 | | | | | | | | | | |
Convertible Debentures | 5.6% Debentures Due June 2017 And 6.25% Debentures Due March 2017 (Member) | Interest expense | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Write-off of deferred financing costs | | | | | | $ 1.3 | | | | | | | |
Convertible Debentures | 5.75% Debentures due June 2019 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | | | 5.75% | | | | | 5.75% | |
Convertible Debentures | 6.00% Debenture due December 2019 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | CAD | | | | | | | CAD 81 | | | | | | |
Interest rate (as a percent) | | | | | | | 6.00% | | | | | 6.00% | |
APLP Holdings | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Amount of cash flow of APLP Holdings and its subsidiaries remaining after application of funds according to the Credit Agreement to be applied under | | | 50 | | | | | | | | 50 | | |
Other percentage of cash flow required to reduce aggregate principal amount of new term loans outstanding to achieve target principal amount that declines | | | 100 | | | | | | | | 100 | | |
APLP Holdings | Subsequent event | Minimum | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Leverage ratio as defined in Credit Agreement | | | 4.25 | | | | | | | | 4.25 | | |
Interest coverage ratio as defined in Credit Agreement | | | 2.75 | | | | | | | | 2.75 | | |
APLP Holdings | Subsequent event | Maximum | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Leverage ratio as defined in Credit Agreement | | | 6 | | | | | | | | 6 | | |
Interest coverage ratio as defined in Credit Agreement | | | 4 | | | | | | | | 4 | | |
APLP Holdings | Interest expense | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Write-off of deferred financing costs | | | | | | $ 30 | | | | | | | |
APLP Holdings | New Term Loans | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Remaining proceeds of New Credit Facility | | | | | | | | | | | | $ 105 | |
APLP Holdings | New Term Loans | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Prepayment of term loans if change of control occurs, as a percentage of par | | | 101 | | | | | | | | 101 | | |
Period from initial funding date that APLP would be required to repay, prepay, refinance or replace at a price of 101 percent of the principal amount if they elect to do so for any portion or all of the term loan facilities | | | 1 year | 1 year | | | | | | | | | |
Percent of principal amount required to be repaid, prepaid, refinanced or replaced if APLP elects to do so within one year of initial funding date | | | 101 | | | | | | | | 101 | | |
APLP Holdings | New Credit Facilities | Minimum | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Margin on variable interest rate | | | | | | | 4.00% | 4.00% | | | | | |
APLP Holdings | New Credit Facilities | New Term Loans | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | | | | | | | | | | | $ 700 | | |
Amount drawn under loan | | | | | | | | | | | 700 | | |
Proceeds from debt, net of discount | | | | $ 679 | | | | | | | | | |
Original issue discount (as a percent) | | | 3.00% | 3.00% | | | | | | | | | |
Original issue discount amount | | | | | | | | | | | 21 | | |
Transaction costs and expenses | | $ 14.4 | | | | | | | | | | | |
APLP Holdings | New Credit Facilities | New Term Loans | Adjusted Eurodollar Rate | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Margin on variable interest rate | | | 5.00% | 5.00% | | | | | | | | | |
APLP Holdings | New Credit Facilities | New Revolver | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | | | | | | | | | | | 200 | | |
Number of days prior to the Letter of Credit Expiration Date that letters of credit are available to be issued | | | 30 days | 30 days | | | | | | | | | |
Commitment fee related to New Revolver, as a percent | | | 0.75% | 0.75% | | | | | | | | | |
APLP Holdings | New Credit Facilities | Letters of credit | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | | | | | | | | | | | $ 105.8 | | |
Period of debt service covered by debt service reserve fund | | | 6 months | 6 months | | | | | | | | | |
Amount of debt service reserve | | | | $ 25.3 | | | | | | | | | |
APLP Holdings | Convertible Debentures | 6.25% Debentures due March 2017 | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Proceeds deposited with trustee in advance of payment of certain unsecured subordinated debentures | CAD | CAD 67.2 | | | | | | | | | | | | |
APLP Holdings | Convertible Debentures | 5.6% Debentures due June 2017 | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Proceeds deposited with trustee in advance of payment of certain unsecured subordinated debentures | CAD | CAD 75.8 | | | | | | | | | | | | |
APLP Holdings | Convertible Debentures | 5.6% Debentures Due June 2017 And 6.25% Debentures Due March 2017 (Member) | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Proceeds deposited with trustee in advance of payment of certain unsecured subordinated debentures | | 111.8 | | | | | | | | | | | |
APLP Holdings | Convertible Debentures | 5.6% Debentures Due June 2017 And 6.25% Debentures Due March 2017 (Member) | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Proceeds deposited with trustee in advance of payment of certain unsecured subordinated debentures | | | | $ 111.8 | | | | | | | | | |
APLP Holdings | Convertible Debentures | 5.75% Debentures due June 2019 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | | | 5.75% | | | | | 5.75% | |
Amount of subordinated debt that may be repurchased with remaining proceeds | | | | | | | | $ 105.3 | | | | | |
APLP Holdings | Convertible Debentures | 6.00% Debenture due December 2019 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | | | 6.00% | | | | | 6.00% | |
Amount of subordinated debt that may be repurchased with remaining proceeds | CAD | | | | | | | CAD 81 | | | | | | |
APLP | New Credit Facilities | Maximum | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Margin on variable interest rate | | | | | | | 5.00% | 5.00% | | | | | |
APLP | Long-term debt excluding debentures | Senior secured term loan, due 2021 | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Redemption of senior secured term loan | | $ 447.9 | | | | | | | | | | | |
APLP | Long-term debt excluding debentures | Senior unsecured notes, due June 2036 (Cdn$210.0) | Subsequent event | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Aggregate principal amount of debt | CAD | | | CAD 210 | | | | | | | | | | |
Interest rate (as a percent) | | | 5.95% | | | | | | | | 5.95% | | |
APLP | Convertible Debentures | 6.25% Debentures due March 2017 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | | | 6.25% | | | | | 6.25% | |
APLP | Convertible Debentures | 5.6% Debentures due June 2017 | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | |
Interest rate (as a percent) | | | | | | | 5.60% | | | | | 5.60% | |