Earnings per Share (Computation of Basic and Diluted Earnings Per Share) (Details) $ / shares in Units, $ in Thousands		3 Months Ended								9 Months Ended	12 Months Ended
		Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / shares	Sep. 30, 2016	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income | $		$ (3,173)	$ 11,339	$ 10,234	$ 10,076	$ 10,902	$ 10,903	$ 9,616	$ 8,646		$ 28,476	$ 40,067	$ 20,952
Dividends and undistributed earnings allocated to participating securities(1) | $	[1]										(118)	(189)	(59)
Net income available to common shareholders | $											$ 28,358	$ 39,878	$ 20,893
Weighted-average common shares outstanding for basic EPS											15,509,665	15,422,160	12,031,294
Dilutive effect of stock-based awards	[2]										78,682	82,079	43,285
Weighted-average common and potential common shares for diluted EPS											15,588,347	15,504,239	12,074,579
Basic EPS | $ / shares		$ (0.20)	$ 0.72	$ 0.66	$ 0.65	$ 0.70	$ 0.70	$ 0.62	$ 0.56		$ 1.83	$ 2.59	$ 1.73
Diluted EPS | $ / shares		$ (0.20)	$ 0.72	$ 0.66	$ 0.64	$ 0.70	$ 0.70	$ 0.62	$ 0.56		$ 1.82	$ 2.57	$ 1.73
Shares that were not considered in computation of potential common shares for purposes of diluted EPS	[3]										0	0	19,875
Stockholders' Equity Note, Stock Split, Conversion Ratio										1.5	1.5

[1] Represents dividends paid and undistributed earnings allocated to nonvested stock-based awards that contain non-forfeitable rights to dividends.

[2] Represents the effect of the assumed exercise of stock options, and vesting of restricted shares and restricted stock units, and issuance of LTIP awards that have met the performance criteria, utilizing the treasury stock method.

[3] Represents stock-based awards not included in the computation of potential common shares for purposes of calculating diluted EPS as the exercise prices were greater than the average market price of the Company's common stock, and, therefore, are considered anti-dilutive.