Stockholders' Equity and Earnings Per Share (Details 3) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Basic
Net income	$ 169,736	$ 107,516
Basic weighted average number of shares outstanding (in shares)	144,249	143,958
Basic EPS (in dollars per share)	$ 1.18	$ 0.75
Diluted
Net income	$ 169,736	$ 107,516
Basic weighted average number of shares outstanding (in shares)	144,249	143,958
Diluted potential common shares (in shares)	1,483	845
Diluted weighted average number of shares outstanding (in shares)	145,732	144,803
Diluted EPS (in dollars per share)	$ 1.16	$ 0.74