Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income (Numerator)
Income available to common stockholders, Basic									$ 320,087	$ (5,728)	$ 144,877
Income available to common stockholders after assumed conversions, Diluted									$ 320,087	$ (5,728)	$ 144,877
Weighted Shares (Denominator)
Weighted shares, basic (in shares)									55,351,000	55,335,000	55,316,000
Weighted shares, diluted (in shares)									55,360,000	55,335,000	55,327,000
Earnings Per Share Basic and Diluted, Per Share Amounts [Abstract]
Basic (in dollars per share)	$ 0.57	$ 1.25	$ 1.50	$ 2.46	$ (1.48)	$ 1.06	$ 1.09	$ (0.77)	$ 5.78	$ (0.10)	$ 2.62
Diluted (in dollars per share)	$ 0.57	$ 1.25	$ 1.50	$ 2.45	$ (1.48)	$ 1.06	$ 1.09	$ (0.77)	$ 5.78	$ (0.10)	$ 2.62
Common Stock [Member]
Earnings Per Share Basic and Diluted, Per Share Amounts [Abstract]
Potentially dilutive securities (in shares)									0	78,500	0
Stock Options [Member]
Income (Numerator)
Effect of dilutive securities: Options									$ 0	$ 0	$ 0
Weighted Shares (Denominator)
Effect of dilutive securities: options (in shares)									9,000	0	11,000