Segment Reporting - Information about Operations in Different Segments (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Loss (gain) on asset disposals		$ (362)		$ 1,910		$ (362)	$ 1,543
Capital expenditures	[1]	138,774		24,013		170,674	47,985
Accrued Capital Expenditures of 2016 [Member]
Segment Reporting Information [Line Items]
Capital expenditures		$ 1,000				2,000
Accrued Capital Expenditures of 2015 [Member]
Segment Reporting Information [Line Items]
Capital expenditures				8,000			11,000
AEA [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges			$ 32,000			$ 32,000
ASA [Member]
Segment Reporting Information [Line Items]
Asset Impairment Charges				7,000	$ 4,000		4,000
Loss (gain) on asset disposals				$ 3,000			$ 3,000

[1] Total capital expenditures represent expenditures for which cash payments were made during the period. Capital expenditures for the three months ended June 30, 2016 included $1 million of cash payments for liabilities outstanding as of March 31, 2016 and for the six months ended June 30, 2016 excluded $2 million in accrued liabilities outstanding at the end of the period. Capital expenditures for the three and six months ended June 30, 2015 included $8 million and $11 million, respectively, of cash payments for accrued capital expenditures outstanding at the end of the respective periods.