Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Net income	$ 63,722	$ 12,631	$ 27,280	$ 20,534	$ 20,427
Less income allocated to non-controlling interests	(89)				(81)
Less income allocated to participating securities:
Non-forfeitable dividends on participating securities	(94)				(92)
Income allocated to participating securities	(169)
Total net income allocated to participating securities	(263)				(92)
Net income available to common stockholders	63,370				20,254
Effect of dilutive securities:
Participating securities					92
Net income for diluted net income per share	$ 63,370				$ 20,346
Reconciliation of shares
Shares for basic net income per share	39,539,000				39,532,000
Effect of dilutive securities: (Shares)
Total effect of dilutive securities (in shares)	2,000				342,000
Shares for diluted net income per share	39,541,000				39,874,000
Basic (in dollars per share)	$ 1.60				$ 0.51
Diluted (in dollars per share)	$ 1.60				$ 0.51
Stock options
Effect of dilutive securities: (Shares)
Stock options and performance-based stock units (in shares)	2,000				4,000
Performance-based stock units
Effect of dilutive securities: (Shares)
Stock options and performance-based stock units (in shares)					181,000
Number of shares granted	0
Participating Securities
Effect of dilutive securities: (Shares)
Participating securities					157,000