Business Combinations - Results of Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	$ 3,191		$ 3,645
Business Combination Pro Forma Information Income Loss Before Income Taxes Of Acquiree Since Acquisition Date Actual	864		979
Total revenues	476,124	$ 465,014	1,413,278	$ 1,341,511
Income before income taxes	124,582	117,929	345,608	331,574
Net income	$ 76,012	$ 72,130	$ 213,496	$ 201,675
Net income per share:
Basic (in dollars per share)	$ 0.54	$ 0.51	$ 1.52	$ 1.44
Diluted (in dollars per share)	$ 0.53	$ 0.51	$ 1.50	$ 1.43
Weighted Average Basic Shares Outstanding, Pro Forma	136,346	136,461	136,592	136,002
Weighted average number of shares outstanding:
Pro Forma Weighted Average Shares Outstanding, Diluted	138,893	138,182	139,011	137,584

Business Combination Pro Forma Information Income Loss Before Income Taxes Of Acquiree Since Acquisition Date Actual

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- Definition

Per basic share amount of pro forma income from continuing operations, after tax, as if the business combination had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

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- Definition

Per diluted share amount of pro forma income from continuing operations, after tax, as if the business combination had been completed at the beginning of a period.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

+ References

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- Definition

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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- Definition

The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

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- Definition

This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

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- Definition

The weighted average number of shares or units and dilutive common stock or unit equivalents outstanding in the calculation of proforma diluted earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

+ References

No definition available.

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- Definition

The weighted average number of shares (units) outstanding in the calculation of pro forma basic earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

+ References

No definition available.

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