Stockholders' Equity (Textual) (Details) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) offering $ / shares Rate shares
Class of Stock [Line Items]
Preferred stock, par value (in usd per share) | $ / shares	$ 1	$ 1	$ 1
Authorized repurchased amount (up to)		$ 100,000,000
Number of shares repurchased | shares	6.8
Total cost of common stock repurchases, including broker commissions	$ 61,500,000
Number of shares issued during period | shares			26.7
Number of stock offerings | offering			2
Proceeds from issuance of stock			$ 321,900,000
Redemption price per share (in usd per share) | $ / shares			$ 25.00
Redemption amount			$ 94,800,000
Original issuance costs applicable to shares redeemed	$ 0	$ 0	$ 3,530,000
Restriction on ownership, percentage (more than) | Rate			3.90%
Preferred Stock
Class of Stock [Line Items]
Number of shares issued in merger | shares	6.9
Series B Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Dividend rate (percent)			7.50%