Other Assets (Detail) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Purchase of held to maturity securities	$ 81.0

Amount of cash outflow through purchase of long-term held-to-maturity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26853-111562

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