Common, Subordinated, Convertible Class B, Subordinated Class C and General Partner Units Issued (Detail)	0 Months Ended	12 Months Ended
	Aug. 15, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Limited Partners Capital Account [Line Items]
Long-term incentive plan awards		903,638	100,248	48,786
Equity issuance			10,561,224	42,303,386
Conversion of subordinated units to common units	69,076,122
ATM equity issuances		927,774	971,765
Paid-in-kind Class B unit distributions		516,336	577,865
Pre-merger unit split rate		0.0106152
Units issued at beginning period		205,535,483	193,324,381	150,972,209
Units issued at ending period		207,883,231	205,535,483	193,324,381
Units issued at ending period		220,672,208
Common Units
Limited Partners Capital Account [Line Items]
Limited partner units issued at ending period		202,532,920	188,739,474
Class B Units
Limited Partners Capital Account [Line Items]
Limited partner units issued at ending period		13,725,843	13,188,705
Class C Units
Limited Partners Capital Account [Line Items]
Limited partner units issued at ending period		0	11,888,247
Limited Partner | Common Units
Limited Partners Capital Account [Line Items]
Limited partner units issued at beginning period		177,801,147	97,324,453	78,876,643
Long-term incentive plan awards		885,565	98,242	47,810
Equity issuance			10,350,000	18,400,000
Limited partner units issued at ending period		202,532,920	177,801,147	97,324,453
Conversion of subordinated units to common units		11,199,268	69,076,122
ATM equity issuances		909,219	952,330
Limited partner units issued excluding pre merger unit split at ending period		190,795,199
Pre-merger unit split rate		1.06152
Limited Partner | Subordinated units
Limited Partners Capital Account [Line Items]
Limited partner units issued at beginning period			69,076,122		69,076,122
Limited partner units issued at ending period					69,076,122
Conversion of subordinated units to common units			(69,076,122)
Limited Partner | Class B Units
Limited Partners Capital Account [Line Items]
Limited partner units issued at beginning period		12,424,358	11,858,050
Equity issuance				11,858,050
Limited partner units issued at ending period		13,725,843	12,424,358	11,858,050
Paid-in-kind Class B unit distributions		506,009	566,308
Limited partner units issued excluding pre merger unit split at ending period		12,930,367
Pre-merger unit split rate		1.06152
Limited Partner | Class C Units
Limited Partners Capital Account [Line Items]
Limited partner units issued at beginning period		11,199,268
Equity issuance				11,199,268
Limited partner units issued at ending period				11,199,268
Conversion of subordinated units to common units		(11,199,268)
General Partner
Limited Partners Capital Account [Line Items]
Long-term incentive plan awards		18,073	2,006	976
Equity issuance			211,224	846,068
ATM equity issuances		18,555	19,435
Paid-in-kind Class B unit distributions		10,327	11,557
Pre-merger unit split rate		0.0106152
Units issued at beginning period		4,110,710	3,866,488	3,019,444
Units issued at ending period		4,157,665	4,110,710	3,866,488
General partner units issued at ending period		4,413,445