Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 40,459	$ 11,484	$ 140,077	$ 60,864
Net income allocated to participating securities	129	37	566	78
Net income allocated to common shareholders	$ 40,330	$ 11,447	$ 139,511	$ 60,786
Weighted average common shares - issued (in shares)	71,139,000	49,109,000	71,077,000	41,881,000
Average unvested restricted share awards (in shares)	(228,000)	(159,000)	(290,000)	(53,000)
Weighted average common shares outstanding - basic (in shares)	70,911,000	48,950,000	70,787,000	41,828,000
Effect of dilutive securities
Weighted average common stock equivalents (in shares)	594,000	687,000	667,000	493,000
Weighted average common shares outstanding - diluted (in shares)	71,505,000	49,637,000	71,454,000	42,321,000
EPS available to common shareholders
Basic earnings per common share (dollars per share)	$ 0.57	$ 0.23	$ 1.98	$ 1.45
Diluted earnings per common share (dollars per share)	0.56	0.23	1.95	1.42
Average stock valuation (dollars per share)	$ 47.68	$ 42.40	$ 49.07	$ 37.85
Stock Option
Schedule Of Earnings Per Share By Common Class [Line Items]
Average number of exercisable employee stock option awards that were not included in the computation of diluted earnings per common share (in shares)	125,280	0	102,245	0