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
Earnings Per Share Reconciliation [Abstract]
Net income	$ 123,023	$ 30,745	$ 32,589	$ 32,449	$ 50,614	$ 30,723	$ 28,479	$ 18,871	$ 218,806	$ 128,687	$ 139,425
Net income available to participating securities									3,496	1,885	1,792
Net earnings available to common shareholders									$ 215,310	$ 126,802	$ 137,633
Basic (in shares)	47,626,833	47,673,211	47,727,786	47,560,749	47,967,014	48,009,953	47,951,326	47,873,007	47,647,397	47,950,746	47,586,242
Dilutive effect of equity incentive plans (in shares)									78,076	146,906	228,166
Dilutive effect of convertible debt (in shares)									1,300,211	830,139	854,619
Diluted (in shares)	49,425,395	49,064,272	49,102,879	48,509,181	48,505,023	49,279,217	49,218,521	48,706,717	49,025,684	48,927,791	48,669,027
Basic (in dollars per share)	$ 2.54	$ 0.63	$ 0.67	$ 0.67	$ 1.04	$ 0.63	$ 0.59	$ 0.39	$ 4.52	$ 2.64	$ 2.89
Earnings Per Share, Diluted	$ 2.45	$ 0.62	$ 0.66	$ 0.66	$ 1.03	$ 0.61	$ 0.57	$ 0.38	$ 4.39	$ 2.59	$ 2.83
Share options excluded from the computation of diluted earnings per share									0	0	0