Stockholders' Equity (Details) - USD ($)					12 Months Ended
	Oct. 02, 2014	Sep. 26, 2014	Feb. 11, 2014	Jan. 10, 2014	Dec. 31, 2014	Dec. 31, 2013	May. 28, 2014
Class of Stock [Line Items]
Stock issued (in shares)					23,716,900	31,049,976
Proceeds from common stock issuance	$ 204,800,000		$ 205,200,000
At-the-Market
Class of Stock [Line Items]
Proceeds from common stock issuance					$ 8,000,000
Common stock amount authorized							$ 150,000,000.0
At-the-Market | Maximum
Class of Stock [Line Items]
Sale commissions on percent of stock sale price (as a percent) (less than)							2.00%
Common Stock
Class of Stock [Line Items]
Stock issued (in shares)	1,500,000	10,000,000	1,325,000	10,500,000
Share price (in dollars per share)	$ 18.60	$ 18.60	$ 18.15	$ 18.15
Common Stock | At-the-Market
Class of Stock [Line Items]
Stock issued (in shares)					391,900
Sales commissions and fees					$ 122,000