Equity - Treasury Stock (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Oct. 26, 2017	May 12, 2014
Equity, Class of Treasury Stock [Line Items]
Authorized share amount for repurchase (up to)			$ 10,000,000
Shares repurchased, value	$ 43,923,000
Brokerage commissions	109,000
Remaining authorizations under the repurchase program	$ 13,000
Shares reissued from the treasury (in shares)	2,684,270
Shares reissued from the treasury, value	$ 24,801,000
Treasury Stock
Equity, Class of Treasury Stock [Line Items]
Share repurchase (in shares)	3,644,327
Shares repurchased for tax withholding (in shares)	358,861
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Authorized share amount for repurchase (up to)		$ 120,000,000