Commitments and Contingencies - Future Minimum Payments under Non-Cancelable Operating Leases and Capital Leases (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
2015	$ 79,994
2016	59,365
2017	47,491
2018	42,084
2019	32,164
Thereafter	27,014
Total minimum lease payments	$ 288,112

Operating Leases and Capital Leases, Future Minimum Payments Due

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDue
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Operating Leases and Capital Leases, Future Minimum Payments, Due in Five Years

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDueinFiveYears
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Operating Leases and Capital Leases, Future Minimum Payments, Due in Four Years

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDueinFourYears
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Operating Leases and Capital Leases, Future Minimum Payments, Due in Three Years

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDueinThreeYears
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Operating Leases and Capital Leases, Future Minimum Payments, Due in Two Years

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDueinTwoYears
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Operating Leases and Capital Leases, Future Minimum Payments Due, Next Twelve Months

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDueNextTwelveMonths
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Operating Leases and Capital Leases, Future Minimum Payments, Due Thereafter

No definition available.

Name:	df_OperatingLeasesandCapitalLeasesFutureMinimumPaymentsDueThereafter
Namespace Prefix:	df_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Name:	us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration