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Subsidiary Guarantors - Schedule of Consolidating Statement of Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	2 Months Ended	3 Months Ended														8 Months Ended		12 Months Ended
	Dec. 31, 2014	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Apr. 30, 2014	Dec. 31, 2013	Apr. 30, 2013	Dec. 31, 2012	Apr. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ (6,017)us-gaap_ProfitLoss	$ 361us-gaap_ProfitLoss	$ (154)us-gaap_ProfitLoss	$ (15,633)us-gaap_ProfitLoss	$ (11,033)us-gaap_ProfitLoss	$ (575)us-gaap_ProfitLoss	$ (163)us-gaap_ProfitLoss	$ (13,518)us-gaap_ProfitLoss	$ (11,474)us-gaap_ProfitLoss	$ (21,092)us-gaap_ProfitLoss	$ (8,379)us-gaap_ProfitLoss	$ (49,130)us-gaap_ProfitLoss	$ (24,635)us-gaap_ProfitLoss	$ (765)us-gaap_ProfitLoss	$ (3,062)us-gaap_ProfitLoss	$ (5,810)us-gaap_ProfitLoss	$ (4,078)us-gaap_ProfitLoss	$ (27,404)us-gaap_ProfitLoss	$ (27,404)us-gaap_ProfitLoss	$ (54,463)us-gaap_ProfitLoss	$ (54,463)us-gaap_ProfitLoss	$ (77,592)us-gaap_ProfitLoss	$ (77,592)us-gaap_ProfitLoss
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments																		(36)	(36)	(2,910)	(2,910)	(1,749)	(1,749)
Realized loss (gain) on derivative instruments reclassified into earnings																		655	655	4,247	4,247	(578)	(578)
Unrealized gain (loss) resulting from changes in fair value of marketable securities																19		12	12	23	23	(3)	(3)
Other comprehensive income (loss																19		631	631	1,360	1,360	(2,330)	(2,330)
Comprehensive income (loss)																(5,791)		(26,773)	(26,773)	(53,103)	(53,103)	(79,922)	(79,922)
Less: Comprehensive income (loss) attributable to noncontrolling interest																208		(4,309)	(4,309)	(321)	(321)	(6)	(6)
Comprehensive income (loss) attributable to common stockholders																(5,999)us-gaap_ComprehensiveIncomeNetOfTax		(22,464)us-gaap_ComprehensiveIncomeNetOfTax	(22,464)us-gaap_ComprehensiveIncomeNetOfTax	(52,782)us-gaap_ComprehensiveIncomeNetOfTax	(52,782)us-gaap_ComprehensiveIncomeNetOfTax	(79,916)us-gaap_ComprehensiveIncomeNetOfTax	(79,916)us-gaap_ComprehensiveIncomeNetOfTax
Transition Period 2014 [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																(5,810)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments																19
Other comprehensive income (loss																19
Comprehensive income (loss)																(5,791)
Less: Comprehensive income (loss) attributable to noncontrolling interest																208
Comprehensive income (loss) attributable to common stockholders																(5,999)
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																(6,018)		(23,095)	(23,095)	(54,142)	(54,142)	(77,586)	(77,586)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments																				(1,257)		(2,253)
Realized loss (gain) on derivative instruments reclassified into earnings																				3,626		(77)
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss																				2,369		(2,330)
Comprehensive income (loss)																		(23,095)		(51,773)		(79,916)
Less: Comprehensive income (loss) attributable to noncontrolling interest
Comprehensive income (loss) attributable to common stockholders																		(23,095)		(51,773)		(79,916)
Parent [Member] \| Transition Period 2014 [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																(6,018)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments
Other comprehensive income (loss
Comprehensive income (loss)																(6,018)
Less: Comprehensive income (loss) attributable to noncontrolling interest
Comprehensive income (loss) attributable to common stockholders																(6,018)
Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																25,926		23,807	23,807	(19,954)	(19,954)	(46,144)	(46,144)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments
Realized loss (gain) on derivative instruments reclassified into earnings
Unrealized gain (loss) resulting from changes in fair value of marketable securities																		12		23		(3)
Other comprehensive income (loss																		12		23		(3)
Comprehensive income (loss)																		23,819		(19,931)		(46,147)
Less: Comprehensive income (loss) attributable to noncontrolling interest
Comprehensive income (loss) attributable to common stockholders																		23,819		(19,931)		(46,147)
Guarantors [Member] \| Transition Period 2014 [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																25,926
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments																19
Other comprehensive income (loss																19
Comprehensive income (loss)																25,945
Less: Comprehensive income (loss) attributable to noncontrolling interest
Comprehensive income (loss) attributable to common stockholders																25,945
Non-Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																430		(9,305)	(9,305)	(5,090)	(5,090)	(20,694)	(20,694)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments																		(36)		(1,653)		504
Realized loss (gain) on derivative instruments reclassified into earnings																		655		621		(501)
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss																		619		(1,032)		3
Comprehensive income (loss)																		(8,686)		(6,122)		(20,691)
Less: Comprehensive income (loss) attributable to noncontrolling interest																		(4,309)		(321)		(6)
Comprehensive income (loss) attributable to common stockholders																		(4,377)		(5,801)		(20,685)
Non-Guarantors [Member] \| Transition Period 2014 [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																430
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments
Other comprehensive income (loss
Comprehensive income (loss)																430
Less: Comprehensive income (loss) attributable to noncontrolling interest																208
Comprehensive income (loss) attributable to common stockholders																222
Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																(26,148)		(18,811)	(18,811)	24,723	24,723	66,832	66,832
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments
Realized loss (gain) on derivative instruments reclassified into earnings
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss
Comprehensive income (loss)																		(18,811)		24,723		66,832
Less: Comprehensive income (loss) attributable to noncontrolling interest
Comprehensive income (loss) attributable to common stockholders																		(18,811)		24,723		66,832
Elimination [Member] \| Transition Period 2014 [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)																(26,148)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments
Other comprehensive income (loss
Comprehensive income (loss)																(26,148)
Less: Comprehensive income (loss) attributable to noncontrolling interest
Comprehensive income (loss) attributable to common stockholders																$ (26,148)