Earnings Per Share - Earnings (Loss) Per Common Share (Detail) - $ / shares	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings per common share—basic
Continuing Operations									$ 2.33	$ 2.29	$ 1.60
Discontinued Operations									0	0.61	0.29
Total Earnings Per Common Share—Basic									2.33	2.90	1.89
Earnings per common share—diluted
Continuing Operations					$ 0.50	$ 0.60	$ 0.58	$ 0.56	2.29	2.24	1.57
Discontinued Operations					0.24	(0.01)	0.00	0.37	0	0.59	0.28
Total Earnings Per Common Share—Diluted	$ 0.80	$ 0.56	$ 0.39	$ 0.53	$ 0.74	$ 0.58	$ 0.58	$ 0.93	$ 2.29	$ 2.83	$ 1.85