Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Summary of Unaudited Quarterly Results of Operations (Parenthetical) (Detail) - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Schedule Of Quarterly Financial Data [Line Items]
U.S. federal statutory corporate tax rate	21.00%	35.00%	31.50%	35.00%	35.00%
Income tax expense			$ 21.4
ASU 2016-09
Schedule Of Quarterly Financial Data [Line Items]
Excess tax benefit			$ 31.0