JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) (l) under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing of the attached Schedule 13G, and any and all amendments thereto, and expressly authorize Invesco Ltd., as the ultimate parent company of each of its undersigned subsidiaries, to file such Schedule 13G, and any and all amendments thereto, on behalf of each of them.

Dated:  12/31/2011

Invesco Ltd.

By: /s/ Lisa Brinkley

Name: Lisa Brinkley

Title: Global Assurance Officer

Invesco Advisers, Inc.

By: /s/ Jeffrey Kupor

Name: Jeffrey Kupor

Title: Senior Vice President

Invesco Canada Ltd.

By: /s/ Wayne Bolton

Name: Wayne Bolton

Title: Vice President, Compliance & Chief Compliance Officer

Invesco National Trust Company

By: /s/ Kevin Lyman

Name: Kevin Lyman

Title: Assistant General Counsel

Invesco Hong Kong Limited

By: /s/ Asha Balachandra

Name: Asha Balachandra

Title: Reg. Head of Legal AP

Invesco Asset Management Deutschland GmbH

By: /s/ Stephanie Ehrenfried

Name: Stephanie Ehrenfried

Title: Head of Legal CE

Invesco Asset Management Limited

By: /s/ Nick Styman

Name: Nick Styman

Title: Director of European Compliance

Invesco Asset Management S.A.

By: /s/ Nicolas Bouet

Name: Nicolas Bouet

Title: Deputy Managing Director

Invesco Asset Management S.A.

By: /s/ Bernard Aybran

Name: Bernard Aybran

Title: Deputy Managing Director

Invesco Asset Management Oesterreich GmbH

By: /s/ Thomas Kraus

Name: Thomas Kraus

Title: Head of Sales

Invesco GT Management Company S.A.

By: /s/ Nick Styman

Name: Nick Styman

Title: Director of European Compliance

Invesco Management S.A.

By: /s/ John Rowland

Name: John Rowland

Title: Director

Invesco Taiwan Limited

By: /s/ Asha Balachandra

Name: Asha Balachandra

Title: Reg. Head of Legal, AP

Invesco Asset Management (Japan) Limited

By: /s/ Asha Balachandra

Name: Asha Balachandra

Title: Reg. Head of Legal, AP

Invesco Asset Management Ireland Limited

By: /s/ John Rowland

Name: John Rowland

Title: Director

Invesco Kapitalanlagegesellschaft GmbH

By: /s/ Stephanie Ehrenfried

Name: Stephanie Ehrenfried

Title: Head of Legal CE

Invesco PowerShares Capital Management LLC

By: /s/ Deanna Marotz

Name: Deanna Marotz

Title: Chief Compliance Officer

Stein Roe Investment Counsel, Inc.

By: /s/ Greg Campbell

Name: Greg Campbell

Title: General Counsel

Invesco Investment Advisers, LLC

By: /s/ Christopher C. Joe

Name: Christopher C. Joe

Title: Chief Compliance Officer