Stockholder's Equity - Changes in the Number of Shares Outstanding and Treasury Shares Held by the Company (Details) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Shares Outstanding [Abstract]
Beginning balance	241,388,277	239,016,924
Common stock issued	2,586,578	1,907,215
Purchase of common stock	(933,060)	(569,999)
Ending balance	243,041,795	240,354,140
Shares Held as Treasury Shares [Abstract]
Beginning balance	8,302,004	7,824,204
Purchase of common stock	933,060	569,999
Retirement of common stock	(787,267)	(373,776)
Ending balance	8,447,797	8,020,427
Common stock, shares issued	251,489,592	248,374,567	249,690,281