Income Per Common Share - Schedule of Basic and Diluted Income Per Common Share Calculation (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
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Basic weighted average number of common shares outstanding (in shares)	37,059,483	36,801,464	37,007,144	36,746,727
Effect of dilutive securities:
Diluted average shares outstanding (in shares)	38,583,341	38,333,027	38,381,292	38,314,021
Net income available to common stockholders	$ 27,418	$ 13,069	$ 36,372	$ 36,644
Basic income per common share (in USD per share)	$ 0.74	$ 0.36	$ 0.98	$ 1.00
Dilutive income per common share (in USD per share)	$ 0.71	$ 0.34	$ 0.95	$ 0.96
Stock Options, Unvested Common Shares, and Warrants
Effect of dilutive securities:
Stock options, unvested common shares, and warrants (in shares)	1,523,858	636,633	1,374,148	672,364
Tangible Equity Units
Effect of dilutive securities:
Tangible equity units (in shares)	0	894,930	0	894,930
Unvested Stock Options
Antidilutive securities not included in the calculation of diluted income per common share (weighted average):
Antidilutive securities (in shares)	240,000	240,000	240,000	240,000
Warrants
Antidilutive securities not included in the calculation of diluted income per common share (weighted average):
Antidilutive securities (in shares)	0	1,907,551	0	1,907,551