Goodwill and Other Intangible Assets - Roll Forward of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Goodwill [Roll Forward]
Balance at beginning of year	$ 175,820us-gaap_GoodwillGross	$ 175,733us-gaap_GoodwillGross
Additions	0us-gaap_GoodwillAcquiredDuringPeriod	87us-gaap_GoodwillAcquiredDuringPeriod
Balance at End of Year	$ 175,820us-gaap_GoodwillGross	$ 175,820us-gaap_GoodwillGross

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration