Income Taxes - Net Operating Loss Carryforwards (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Excess tax benefits from employee stock option exercises, equity increase	$ 7.2
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	205.3
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 109.6

The tax effects of employee stock option transactions that are recognized differently for financial reporting and tax purposes, occurring during the period and charged or credited directly to shareholders' equity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 740
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=65880886&loc=d3e23586-113945

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 740
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=65880886&loc=d3e23594-113945

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=65896914&loc=d3e39076-109324

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