Derivatives and Fair Value Measurements - Paid to and Received from Counterparties for Settlements of Matured Swaps (Detail) - Jun. 30, 2015 - USD ($) $ in Thousands	Total	Total	Total
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Paid to counterparties	$ 690	$ 4,660	$ 5,474
Received from counterparties	$ 0	$ 0	$ 198

The cash inflow provided by derivative instruments during the period, which are classified as investing activities, excluding those designated as hedging instruments.

No definition available.

Name:	us-gaap_ProceedsFromDerivativeInstrumentInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration