Annual report pursuant to Section 13 and 15(d)

Retirement Plans (Details)

v2.4.1.9
Retirement Plans (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]    
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent 50.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent  
Defined Contribution Plan, Employer Matching Contribution, Percent 100.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent  
Defined Contribution Plan Employer Matching Contribution At Fifty Percent 50.00%pdii_DefinedContributionPlanEmployerMatchingContributionAtFiftyPercent  
Pension and Other Postretirement Benefit Expense $ 0.9us-gaap_PensionAndOtherPostretirementBenefitExpense $ 0.7us-gaap_PensionAndOtherPostretirementBenefitExpense
Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Defined Contribution Plan, Employer Matching Contribution, Percent 3.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Defined Contribution Plan Employer Matching Contribution At Fifty Percent 5.00%pdii_DefinedContributionPlanEmployerMatchingContributionAtFiftyPercent
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Minimum [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Defined Contribution Plan Employer Matching Contribution At Fifty Percent 3.00%pdii_DefinedContributionPlanEmployerMatchingContributionAtFiftyPercent
/ us-gaap_RangeAxis
= us-gaap_MinimumMember