Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Long-term Debt, Excluding Current Maturities	$ 973,339		$ 973,339		$ 502,539
Earnings Per Share, Basic [Abstract]
Net income attributable to controlling interests and available to common shareholders	15,158	$ 20,148	14,257	$ 35,532
Less: Undistributed earnings allocated to unvested RSAs	(2)	(10)	(2)	(23)
Net income available to common shareholders	15,156	20,138	14,255	35,509
Earnings Per Share, Diluted [Abstract]
Add: Undistributed earnings allocated to restricted shares, Diluted	2	10	2	23
Less: Undistributed earnings reallocated to RSAs	(1)	(10)	(2)	(22)
Net income available to common shareholders and assumed conversions	$ 15,157	$ 20,138	$ 14,255	$ 35,510
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted Average Shares Outstanding, Basic	45,637,778	45,199,450	45,564,527	45,136,553
Stock options added to the denominator under the treasury stock method	5,662	32,289	8,290	33,073
RSUs added to the denominator under the treasury stock method	578,672	516,831	699,374	534,848
Weighted Average Shares Outstanding, Diluted	46,222,112	45,748,570	46,272,191	45,704,474
Net income per common share - basic	$ 0.33	$ 0.45	$ 0.31	$ 0.79
Net income per common share - diluted	$ 0.33	$ 0.44	$ 0.31	$ 0.78
Restricted Stock Awards [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Antidilutive shares excluded from computation of diluted earnings per share	4,185	11,456	5,644	14,828
Convertible Senior Notes 1.00 percent due 2020
Long-term Debt, Excluding Current Maturities	$ 246,444		$ 246,444		$ 241,068
Debt Instrument, Interest Rate, Stated Percentage	1.00%		1.00%		1.00%