Stockholders' Equity - Share Repurchase Program (Details) - Share repurchase program December 2013 - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2013
Shareholders' Equity
Total purchases authorized under share repurchase program			$ 150.0
Shares repurchased	518,576
Average purchase price (in dollars per share)	$ 15.81
Amount of remaining authorization to repurchase common stock		$ 64.1

Number of shares that have been repurchased during the period and are being held in treasury.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration