Stock-Based Compensation Plans - Additional Information 3 (Detail) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Deferred compensation plan vesting period			3 years
Deferred compensation plan	$ (7,282)	$ 10,519	$ (12,906)	$ 8,484
Shares held in rabbi trust total	2.8		2.8		2.8
Vested shares held in rabbi trust	2.4		2.4		2.5

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 710

-SubTopic 10

-Section 30

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

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