Investments and Other Assets - Additional Information (Detail) - Colorado Corporation [Member] $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Schedule of Cost-method Investments [Line Items]
Cost method investment, ownership percentage	10.00%
Purchase of investments	$ 10.0

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration