Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Earnings Per Share, Basic [Abstract]
Net income attributable to controlling interests and available to common stockholders	$ 27,490	$ 22,009	$ 63,022	$ 52,239
Less: Undistributed earnings allocated to unvested RSAs	(9)	(28)	(34)	(79)
Net income available to common stockholders	27,481	21,981	62,988	52,160
Earnings Per Share, Diluted [Abstract]
Add: Undistributed earnings allocated to restricted shares, Diluted	9	28	34	79
Less: Undistributed earnings reallocated to RSAs	(9)	(27)	(33)	(78)
Net income available to common stockholders and assumed conversions	$ 27,481	$ 21,982	$ 62,989	$ 52,161
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted Average Shares Outstanding, Basic	45,252,869	44,833,117	45,175,604	44,769,661
Stock options added to the denominator under the treasury stock method	20,557	60,693	29,451	68,245
RSUs added to the denominator under the treasury stock method	576,635	497,857	560,180	485,878
Weighted Average Shares Outstanding, Diluted	45,850,061	45,391,667	45,765,235	45,323,784
Net income per common share - basic	$ 0.61	$ 0.49	$ 1.39	$ 1.17
Net income per common share - diluted	$ 0.60	$ 0.48	$ 1.38	$ 1.15
Restricted Stock Awards
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Antidilutive shares excluded from computation of diluted earnings per share	7,217	27,052	12,920	32,106
Convertible Senior Notes 1.00 percent due 2020 [Member]
Long-term Debt.	$ 238,436		$ 238,436		$ 230,754
Debt Instrument, Interest Rate, Stated Percentage	1.00%		1.00%