Capital Structure (Rollforward - Details 1) - shares	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2012
Capital Structure
Preferred stock, shares authorized		10,000,000	10,000,000	10,000,000	10,000,000
Common stock, shares authorized		500,000,000	500,000,000	500,000,000	500,000,000
2.822% convertible perpetual preferred stock, shares issued		0	250,000
2.822% convertible perpetual preferred stock, shares outstanding		0	250,000
Increase (Decrease) in Stockholders' Equity (in shares)
Beginning balance, common shares issued	417,583,825	416,939,950
Beginning balance, treasury shares	(102,140,814)	(102,749,908)
Beginning balance, common shares outstanding	315,443,011	314,190,042
Ending balance, common shares issued		417,583,825	416,939,950
Ending balance, treasury shares		(102,140,814)	(102,749,908)
Ending balance, common shares outstanding		315,443,011	314,190,042
Common Stock
Increase (Decrease) in Stockholders' Equity (in shares)
Beginning balance, common shares issued	417,583,825	416,939,950	415,506,176	401,126,780
Beginning balance, common shares outstanding	315,443,011	314,190,042	336,662,624	323,779,252
Shares issued under ESPP		609,094	283,139	128,336
Shares issued from LTIP		643,875	1,433,774	1,707,419
Stock Repurchased During Period, Shares			24,189,495	1,624,360
Ending balance, common shares issued		417,583,825	416,939,950	415,506,176
Ending balance, common shares outstanding		315,443,011	314,190,042	336,662,624
Treasury Stock
Increase (Decrease) in Stockholders' Equity (in shares)
Beginning balance, treasury shares	102,140,814	102,749,908	78,843,552	77,347,528
Shares issued under ESPP		609,094	283,139	128,336
Shares issued from LTIP		0	0	0
Stock Repurchased During Period, Shares			24,189,495	1,624,360
Ending balance, treasury shares		102,140,814	102,749,908	78,843,552
EME [Member]
Increase (Decrease) in Stockholders' Equity (in shares)
Shares issued in connection with the EME acquisition				12,671,977
EME [Member] | Common Stock
Increase (Decrease) in Stockholders' Equity (in shares)
Shares issued in connection with the EME acquisition				12,671,977
EME [Member] | Treasury Stock
Increase (Decrease) in Stockholders' Equity (in shares)
Shares issued in connection with the EME acquisition				0
Subsequent Event [Member] | Common Stock
Increase (Decrease) in Stockholders' Equity (in shares)
Shares issued under ESPP	282,530