Stockholders' Equity of the Company (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Feb. 23, 2016	Dec. 31, 2015
Common Stock of the Company [Abstract]
At the market stock offering aggregate gross sales price of common stock	$ 300.0
Shares issued to date	92,229,464		92,258,690
Number of shares authorized for repurchase		4,000,000
Remaining number of shares authorized for repurchase	4,935,826	4,988,025
Number of shares repurchased during period	52,199
Weighted average price paid per share repurchased during period	$ 55.45
Value of shares repurchased during period	$ 2.9
Common Stock [Member]
Common Stock of the Company [Abstract]
Issuance of common stock during period, shares	0
At the market stock offering remaining amount available for issuance	$ 149.9
Issuance of Equity - at the market offering [Member] | Common Stock [Member]
Common Stock of the Company [Abstract]
At the market stock offering aggregate gross sales price of common stock	$ 150.1
Shares issued to date	2,007,767