Stockholders' Equity - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended	6 Months Ended
	May 17, 2017	Apr. 30, 2017	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Feb. 25, 2016
Equity [Abstract]
Common stock dividends paid		$ 59,400,000		$ 118,800,000	$ 104,900,000
Dividends paid per common share (in dollars per share)	$ 0.63
Stock repurchase program, authorized amount						$ 200,000,000
Number of shares of common stock repurchased			0	0