Shareholders' Equity - Prospectus Supplement (Details) - USD ($)				9 Months Ended	12 Months Ended
	Mar. 13, 2017	Mar. 08, 2017	Mar. 07, 2017	Sep. 30, 2017	Dec. 31, 2016	Nov. 10, 2014
Class of Stock [Line Items]
New issues (shares)	10,350,000		9,000,000
Common stock, par value (in dollars per share)			$ 0.01	$ 0.01	$ 0.01
Sale of stock, price per share (in dollars per share)			27.8
Proceeds from issuance of common stock	$ 288,100,000
Over-Allotment Option
Class of Stock [Line Items]
Proceeds from issuance of common stock	$ 37,600,000
Prospectus Supplement
Class of Stock [Line Items]
New issues (shares)				0	0
Maximum common stock value authorized under prospectus supplement						$ 150,000,000
Underwriters
Class of Stock [Line Items]
Sale of stock, price per share (in dollars per share)			$ 26.7
Underwriters | Over-Allotment Option
Class of Stock [Line Items]
New issues (shares)		1,350,000
Additional purchase of shares, exercise term			30 days