Segment Reporting - Information about Operations in Different Segments (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended					9 Months Ended
		Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Loss (gain) on asset disposals		$ (588)		$ (100)			$ (950)	$ 1,443
Capital expenditures	[1]	26,719		18,133			197,393	66,118
Accrued Capital Expenditures of 2016 [Member]
Segment Reporting Information [Line Items]
Capital expenditures		$ 2,000					100
Accrued Capital Expenditures of 2015 [Member]
Segment Reporting Information [Line Items]
Capital expenditures				$ 1,000				10,000
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	$ 12,000	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 and nine months ended September 30, 2016 included $2 million and $0.1 million of cash payments for liabilities outstanding at the beginning of the respective periods. Capital expenditures for the three and nine months ended September 30, 2015 included $1 million and $10 million, respectively, of cash payments for accrued capital expenditures outstanding at the beginning of the respective periods.