Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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

Stock Compensation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Noncash payments for repurchase of common stock	$ 400	$ 15	$ 6,900	$ 3,200
Minimum \| Stock Incentive Plan \| Performance share awards
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period			2 years
Maximum \| Stock Incentive Plan \| Performance share awards
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period			3 years