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Stockholders' Equity - Common Share Repurchases and Issuances (Detail) - $ / shares | 3 Months Ended
--- | ---
Mar. 31, 2017 | Mar. 31, 2016
Equity, Class of Treasury Stock [Line Items] |  |
Average purchase price per share | $ 14.95 | $ 10.42
Shares repurchased related to employee stock-based compensation plans | 1,354,280 | 986,273
Average purchase price per share | $ 15.55 | $ 9.96
Common shares issued | 2,794,510 | 2,499,585
Common Stock Shares Outstanding [Member] |  |
Equity, Class of Treasury Stock [Line Items] |  |
Common shares repurchased | 7,363,292 | 19,210,281
Shares repurchased related to employee stock-based compensation plans | 1,354,280 | 986,273
Common shares issued | 2,794,510 | 2,499,585

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- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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